I think I like Nurgle's plan the best by a good margin....but I REALLY don't like the flaws of thunder thing, both IC and OOC
OOC: anything that a game's DM doesn't like (and I recall Durin has said he regrets giving us the action) (even if not enough to force-remove it) is not something I like almost on principle. (and for practical reasons as below...)
IC: ...also he has stated if I recall correctly that it might not even pay off....so we spend however many decades on the first part and get nothing or near-nothing......move on to the next multi decade part and then the next....who knows how many times and each time getting very little.....
....and then we might not even get anything for it!
the fact that the payoff is so uncertain means that they would have to be such a hard-upgrade over SM's for it to statistically be worth it. So the average expected payoff is just so low except under such extreme circumstances that it's just not believable.
the idea that we can take TW's, an prototype-design of a divine/near-divine level bio-engineer, and add something that would outweigh the additions that a near-divine level warp-engineer (who happens to be the same person) added to the same design (to get the SM's) and even sacrificed part of his near-divine level warp-nature to empower them? it's just not reasonable even if we could afford to throw as much time as emp's probably did (which I don't think we can)
instead, is there some creature or another that we could look into instead? we do have a long pile up I believe. and even if they are pretty inconsistent researches, they are much shorter then the mega-tech line that the thunder-line is and so won't tie our biologis up for decades/centurys before payoff (that, again, might not even exist!)
OOC 2: I would also note that durin not liking them is probably more cause to suspect that they might not pay off since DM's are far more forgiving/rewarding with actions if they like the action. (although durin does seem the type to be fair, I don't think anyone can be perfectly fair so its still at least somewhat relevent to consider.)