I think we have very different ideas on what kind of Services we would be offering for the fruit of unimaginable power. I mean if we insert clauses not to ask something which goes against our morals then what exactly is left for the dragon to ask? Do we expect it to give us the fruit for something as small as scratching an itch on it's back or offering it food (what priceless service are you thinking we may owe/offer the dragon). The moment we insert a clause that stipulates that we won't perform a service that goes against our morals becomes the moment that we either have to offer a multitude of services/sacrifices, hope it has one really big morally acceptable service within our capabilities in mind, or give up (what does a 9/10 year old genuinely have to offer right now, how long do we think this Dragon is willing to wait before it calls in its I.O.U., and what guarantee do we or it have that we would be able to perform whatever service it asks of us at a later date). After all the dragon said two things that I feel you don't give enough weight to.
"Every great power comes with an even greater price."
and
"So, what have you decided? How resolute is your will?"
The magic fruit we ate was just short of a free divine blessing the first time around and I think we can all agree that it was sheer dumb luck that we even managed that in the first place (ie the first time we found it we where looking for shelter from a storm and bumbled into it, it wasn't until the second time that we actively sought it out). Now that we are actually bargaining for another I think we should admit that it's not going to be cheap or easy ( and it really shouldn't be).
All this statement brings to mind is that Loki quest I was reading a while back in which every one started complaining about the unintended consequences of the choices they made even if they rolled well or rolled terribly. This is a quest and while no one wants to lose a quest depending on the circumstances and decisions a bad roll is all that is necessary to lose (no one wants to lose but winning isn't a guarantee and we can't expect the DM to bend over backwards every time something doesn't go our way). A 9/10 year old Severus getting a Dragon angry at him is in my mind suicidal and the fact that so far we've mostly met with epic success or hard failure then it seems like this one choice may well be do or die (without knowing how high the roll necessary for success is we have no way of knowing how cushy our safety net is).
Flat out leaving is 1 choice. The second choice is a write in and can be anything you offer. As far as I'm concerned offering to become the dragon's student may well be unexpected enough to work and can be tied in to the fruit to still be within the 2 options (ie Since I don't know you enough to know what to offer, but we know fate ((and possibly something divine)) favors me enough that it may take exception to you harming me how about you take me on as a student on the condition I only get a second fruit with your blessing). I honestly have no idea why you don't think learning from this dragon wouldn't be worth-while.
None of these are even close to guaranteed and the fact that you talk about it so casually is insulting. Besides your statement being made on the assumption that the big three would want to train us there are other problems as well. We already know that the DM has changed some things from Canon so for all we know Dumbledore (the man who was most likely to actually train is out of the kindness of his heart) may well attempt to kill us if he senses our potential and we end up sorted into Slytherin rather than risk us joining Voldemort or Grindelwald (assuming the three aren't secretly working together) or making our own faction. That's ignoring the equally likely possibility that he is so rigidly light that he unintentionally handicaps us or he tries to groom us Potter style in order to have us sacrifice our selves to see the other 2 defeated. Voldemort on the other hand (at least in canon) would not willingly suffer an equal and on the remote chance he doesn't kill Severus for his potential to become his equal, or at the very least a credible threat, is unlikely to ever truly wish to see him realize his full potential if he can't somehow guarantee his subservience (ie unbreakable vow or body jacking us) and this doesn't even take into account that if he even suspected we would join one of the other 2 factions or make our own he'd see us dead in a heartbeat. Truth be told Grindelwald may well be the best teacher option of the three that we can hope for ( ie his politics are terrifying but at least he is not so rigidly light or dark, as Dumbledore and Voldemort where or may be, and he may not mind if Severus becomes stronger than him since even he isn't willing, at least in canon, to make a Horcrux and may well truly wish to groom you into a possible successor, which means he can't slack in your training) and he may well be willing to train you so long as you guarantee your neutrality with him (ie feel free to fight with or deal with the other two to your content just leave me alone and I'll leave you alone). Also when you consider that at least Dumbledore and Voldemort where high tier Legilimens and we can't hope to join/trick them into training us until we become good enough Occlumens to trick them (if necessary) into thinking we genuinely agree with them. Also what exactly are you thinking (do you know something I don't) that you think learning from a (possibly Heretical) Peverel or Merlin is even an option. That's like me claiming that the Dragon is or may be Merlin in disguise (ie completely baseless but possible). As far as I'm concerned (especially after what we recently learned of the Blacks and Petunia) we are not the only kids of our generation that have been exceptionally/oddly gifted to the point the big three wizards are going to be tripping over themselves to gain our favor/allegiance and therefore we can't overly rely on being able to stand out especially since all standing out would do is guarantee the attention of our betters (not their protection or willingness to train us). I would also point out that the big three wizards aren't nearly as, inherently, invested in Severus as Ptolemy is. Ptolemy is, admittedly distant, family and at the very least is far more likely to care more for Severus' safety, success, and goals then anyone else since the continuation of Severus and House Prince are by and large more likely to take priority in his views/agenda then for any of the other three whereas the other three are unlikely to truly train us unless we submit ourselves to their agenda and as such we should be looking for just about anyone else besides them to train us if only to keep ourselves unentangled for as long as possible and give ourselves time to truly come into our own. Honestly it sounds like your POV is colored in a sense that Severus is amazing and has great potential right now and as such any of the other three wizards should be honored/excited by the possibility of being the one to train him if only because every true teacher is inherently delighted by the opportunity to mentor a pupil/successor to surpass them rather than the possibility that some people may well rather see his potential stifled or prematurely ended rather than realized.
Again this assumes we would be able to return a third time and that much of what Ptolemy has to teach isn't outdated or capable of being taught elsewhere (ie a rare spell that may have been kept secret in his time may be common knowledge, perhaps even improved upon, today). This dragon (assuming it isn't someone/thing else in disguise) is more likely to be politically neutral than any other wizard who might take an interest in us, and therefore more invested in us as a student/person rather than a means to further its agenda than anyone else outside of Ptolemy (or your mother).
I would also like to point out that considering Grindelwald's followers are at least aware of, and interested in, Lily and therefore should be peripherally aware of Petunia (we caught/discovered that she is a shapeshifter so unless they epically failed their perception rolls they should be aware of it) and possibly even Severus. If they are in fact aware of Severus but still for some reason prioritize Lily then she is either so amazing as to make Severus look ordinary/plain, somehow needed for some other reason, or being used as a hostage to get Petunia to bait Severus. As such we may soon start running out of options for staying unentangled.
