Intriguing, but two suggestions:
(1) From a realpolitik point of view, what in the world does the Rim Collection offer that would allow them an equal position in the alliance? Unless they're there as a FedCom satellite, and a backdoor way for the Fox to get another vote in the Coalition (like France and Nationalist China in the original UN charter). ComStar clearly has two votes with FRR. The Combine might be considering the OA to be their proxy second vote. St Ives is clearly a FedCom vote in nearly all cases.
The setup currently looks like three big actual manufacturing and military powers, and four really, really marginal military and economic powers.
That said, this makes Sun Tzu's moves in the Third Marik Civil War completely logical. Taking over the FWL, and allying with Canopus in the process, is the only realistic way to counterbalance what the Fox is trying to do to consolidate political and economic control over the Inner Sphere. I'm sure the Combine traditionalists are not thrilled either, but with the Clan threat so imminent (and so long-term, based on the fluff about the full 18/17-clan invasion in this AU), they probably don't have a lot of realistic alternatives.
At least OA participation in general makes sense -- the alliance desperately needs skilled pilots, particularly if they're worried about increased border raids by the Clans, and the OA has plenty of veteran pilots (of the Aerospace variety at least). In exchange, the OA would get better gear and fighters out of the deal. If the Calderons weren't paranoid about the Davions, it would be in their best interest to help out as well, and the Canopians seem to be putting their money on Sun Tzu and taking a chunk out of Andurien in the Third Marik Civil War.
(2) Okay, "bright young minds" is fine, but I only see a few on that list that are worth including: Victor, Hohiro, and Kai (though Kai in the fluff isn't all that great a commander, even if he is a brilliant individual 'Mechwarrior). I like Jerry Able and his fluff, but he's older than the others, he doesn't seem to have any unique strategic or tactical skills although I don't doubt his leadership of the Aces, and most importantly -- the RC can't afford to have him gallivanting off and getting un-alive fighting the Clan. He and the Aces are effectively their entire permanent military!
Mitchell by canon is not a military mind in the slightest, and Hannsen is a complete nobody, who seems to be on the list because he's the son of the interim head of the FRR. And you're missing a ComStar bright young mind, though I suppose your New Earth Precentor character might be the guy? We could probably trawl through the ComStar sourcebooks to find some canon young commanders.
The bigger oddity isn't the inclusion of the n00bs, it's how much of a testosterone party the overall list is, given that you've also got canon young female commanders like Maeve Wolf, who is very definitely up and about right now. What are the Dragoons doing in the Salient Horizon setting? Are they an independent member of this coalition, or are they legally part of the FedCom as the governing body of Outreach? Will there be an anti-Clan version of the Allied Mercenary Command?
There's also Anika Janssen, who's technically a Clan Wolf bondsman in canon, but I can absolutely see the sneaky Wolves letting her escape (or her just escaping, etc) -- or the AU simply noting that she was never captured when the Third Drakon was wiped. As a future (in canon) ComStar Precentor, she's well positioned to be a player in a situation like this. Given that there's a well-developed canon Rasalhague character, why try to write up a complete nobody like Hannsen?
Then there's Ariana Winston (commander of the Eridani Light Horse), and Andrea Stirling (Northwind Highlanders), both well-established canon characters.
As for big Jihad-era names, in 3053, Belle Lee, Danai Centrella, and Alys Marik are still tweeners, but by the time the Clan Invasion kicks off again, they'll be old enough to make an impact.
Last point -- if Hanse has seen the future, he'll clearly know just how much of a colossal f'up his son Victor is. The guy is stunningly incompetent at every possible aspect of rulership, with the only exception being his military skills. Victor's incompetence is pretty much responsible for the entire FedCom civil war in canon, the split with the Combine after years of detente, and indirectly responsible for the Wars of Reaving after the stupid conclusion to Task Force Serpent. He even dies because he's an incompetent -- who tries to investigate and stop a military coup by his 104-year-old lonesome, instead of using his political position to at least bring along some backup? I've never seen Hanse as being a sentimental kind of guy -- if Victor is his sacrificial lamb, given to the alliance (and intended to be thrown at the Clans, possibly to get killed in the process), then which of his remaining kids is he going to groom to replace Victor? Peter is an 18yo moron, Arthur is idealistic and easily manipulated (plus only 16), Katherine even by 21 is a narcissistic sociopath (Hanse even mentions this in chapter one of your fluff!) -- so the baby, 14 yo Yvonne is probably his best bet. Which I find oddly hilarious given her character arc in canon, a character arc that Hanse has apparently witnessed in its entirety.