1) You speak as though "Getting a second Relic Warship" is something that's something to be actually discarded for benefit, rather than an enormous investment in opportunity cost. Five points is a colossal outlay of material, and getting that without paying a heavy price somewhere else is not an exchange I'm willing to make. One big stick from completing an industrial questline--which we are well equipped to complete--should suffice for our needs unless we're going to yolo into a live World Engine during the Great Crusade Era--I don't think our position is that desperate.
1) Even at their weakest (like right now, unshielded and only with tertiary weaponry), a SINGLE one of those relic warships is able to take on a sizeable fraction of the gloriana class battleships (y'know, the flagships of the PRIMARCHS) BY THEMSELVES, meaning that when screened by a decent fleet, we would not have to worry about any kind of naval assault.
Even if we never upgrade them, that ALONE is a massive power boost that is worth the point expendediture and means that we would have to be treated with a healthy amount of caution.
2) Recall that this is our starting position, not something we're straightjacketed forever on. I made the conscious choice to make our starting fleet weighted on Escorts, and not especially sizable to begin with, because I don't intend to start with us surrounded by enemies. The Halo Stars are not an area that is particularly spicy in the Great Crusade Era, at least not to the degree that we're constantly under siege. This is a tactical risk I'm taking here in order to potentially gain much while we work on our Pact Quest Lines to build up experience--both in naval war and conventional war. We should be able to sate the Disarm the Ork Bomb urge too by assisting Meros out of their calamity, which is reward enough. A defensive battle with a friendly base that has an industrial problem is our ideal starting campaign zone to get experience with.
2) I agree that this is our STARTING position and thus is not really locking us to anything, but you are banking WAY too much on the idea that we'll be perfectly safe inside the halo stars and that we won't be bothered by anything, just because we didn't see a threat in canon doesn't mean that we won't see one now in the quest.
Also off topic, but building up a fleet to even a large size could take time that we might not have at our disposal or production we just can't spare.
Also circling back to the starting choice thing, but one plan features a strategy of proactive actions using a large fleet right out of the bat to effectively complete our goals - whatever they may be - and the other is relying on the T'au method of defense (being too small and far away to be worth the effort) to start off with, and ceding the first move to the opponent is a HORRIBLE strategic idea if you want to win (or in this case, survive).
3) The Imperium of Man is far away, the Drukhari are scattered warbands still figuring out what works and what doesn't, and Biel-Tan has Problems of its own in the early days. We're satisfying the "Purge the Orks" impulse with the Meros Campaign, which means we're going to be able to justify laying low and licking our wounds for a while, while at the same time correcting our starting limitations by working on the Pact quest lines to gain allies and battle experience. More importantly, Biel-Tan isn't going to be able to justify Kinstrife without inviting a coalition of Saim-Hann and Iyanden to check them (And Ulthwe will probably tiebreak in favor of "Don't fucking kill each other you idiots"), and they shouldn't have the spare dudes to sneak a deniable op in during the early days while we're entrenching.
3) Just because the Drukhari are not a united force
yet doesn't mean that there might not be a warband (or coalition or warbands) testing our defenses.
Biel-Tan has problems, yes, but we'll have angered them enough that they WILL be mobilising against us, and that means at least one fleet + warhost coming after us, and true, they might not make it in time before we complete arach-qin and upscale our fleet, but what if they
do? The fleet won't be ready to deal with a numerically superior eldar force and by that point, we'll be relying upon Saim-Hann and Iyanden trying to stop the war while Alatoic could probably indirectly support Biel-Tan's efforts somehow.
Also, if Biel-Tan has the manpower to throw a swordwind at us, they will undoubtedly have the manpower and time to fabricate a believable false-flag narrative if they're THAT determined to kill us (which they probably are, since they will trying to kill us as soon as they can get to us).
Purging the orks is as easy as just finding some random planet and fighting some feral orks, so if we have to satisfy that, then we could have options available to us.
Hell, that might even be enough to give us combat experience, and if not, then we can just attack some maiden world full of xenos and get it that way.
We're a sleeping giant that's stirring to wakefulness, and most of my choices are made with purpose to cede tactical ground to make strategic gain through controlled risk-taking.
It is not "risk taking" and we are not "sleeping giants" by turtling up in the halo stars, it's expecting things to NOT go wrong in a Warhammer setting and hoping that we get the breathing room we need to build up to that power, in addition it'll also temporarily limit the amount of military choices we'd have at our disposal.
Also it feels like you're VASTLY overestimating Meros, Zahr-Tahn and Arach-Qin's size (two minors and a small) and their relevance beyond the immediate reward for our services, those allies are DEFINITELY not anywhere close to matching a Major craftworld in I.M.F (Industry, Military, Fleet).
The thing is, this is a plan that doesn't NEED to take such risks, you could've gotten rid of power weapons and replaced Necron respect with fear and you'd have atleast a large sized fleet at your disposal.
To put it crassly (and I am sorry in advance for saying it like this) but there is a difference between taking a risk in the hope of your gambit paying off, and effectively gimping yourself in the short term for no real reason.
Or in other words, you're gambling when you don't
have to and I don't understand why.
(If your choices are strictly for roleplaying purposes then yeah that's understandable)