So, I worked it out, and, without breaking the treaty we have with the Imperium, or warring with the Tau, Eldar, Lizardmen(not sure why we would with the latter two, to be honest), or Necrons we can take 21 more of the Vay-Gir TPs, for 25 total, at which point the Imperium would likely attack us anyway over the perceived threat.
As for Nimrod as a whole, we of course have the 31 Virgin TPs, and the extant 8 Tian'Chaoren and 10 Ogor TPs to federate with. That's 49 of Nimrod's 161 right there. Accounting for enemy TPs nobody who isn't an existing enemy will give a shit about us for killing and taking their land(so not the Advent, Votann, Necrons, Itzecan, Asahikyojin, or Imperium, and ignoring the Thyrrus as we are explicitly advised to do) adds up to another 53(Orks, Dawi Zharr, Rak'gol, Word Bearers, Sarhuadin, Undead, Tyranids, and Numerians) or 102 in total, and if this section of the Imperium is dumb enough to attack us because that would result in us surrounding them from every direction but their southwest corner where the Thyrrus are sitting, that jumps to 111 of 163, more than enough to say that the locale is dominated by the Tian'Chaoren, and probably around the point where we get moved up to a different scale since we dominate the area more or less by existing if we've got more involved per TP than a flag planted in various places.
The Virgin TPs would cost 4650 for Ridiculous Heartlands. The Unfederated TPs are going to depend on their extant buildup and defenses, so it's impossible to know for sure, but the remaining enemy TPs would be 53 normal price TPs, so 2385 for Heartlands-ing them, 1590 for Ridiculous Defenses for all of them, meaning 3975 total, which is significantly less than 31 Virgin TPs. On the other hand, we don't have to conquer the former, and thus have no reason to worry about military expenses from fleet losses, and probably won't make enemies in doing so. In total, it would be 8625, plus whatever pushing the Ogor and currently Unfederated Tian'Chao TPs to their maximums would cost. About 13.6 times our current per Turn income after upkeep.
So, in order, the Production(assuming filled out POPs) of Dominated Vay-Gir(25/27/30/32 TPs under our control, depending on if we conquer the local Imperial and Necron holdings when the former inevitably attacks and we get sick of tithing to the latter) is 1562.5/1687.5/1875/2000, subsuming the Virgin TPs of Nimrod(35 total) would be 2187.5 RP, conquering the straight enemy TPs of Nimrod(53/59/62/68, depending on if you count the Imperium and Necrons among these potential conquests) 3312.5/3687.5/3875/4250. The combination of the least extent of Dominated Vay-Gir and the Virgin TPs of Nimrod would be 56 TPs, with a Production of 3500 RP, while the greatest extent would be 63, producing 3937.5 RP. The combined least extent of Dominated Vay-Gir and the least extent of conquered Enemy TP in Nimrod would be 78 TPs, making 4875 RP, while the greatest extents would be 100 TPs even, producing 6250.
Finally the combined least extent of Dominated Vay-Gir, and the Virgin and potential conquest TPs of Nimrod would be 109, producing 6812.5, and the greatest extent of those would be 131, making 8187.5 RP. Civilian Sector Efficiency and Communications Improvement would make this into 13,509.375 RP.
Of course, if we don't get those techs(or some significant discounts), that's only enough to make 10 Mag 6 Fleets(costing 4000 RP) though we can maintain up to Mag 8(Upkeep of 4000) such Fleets. The techs push that to Mag 7 fleets constructed in one Turn(10,000 RP total) while we can maintain Mag 9(8000), and yes, this has once again devolved into prioritizing our production upgrade techs.