Me, i´ve mostly played as Dracs, Lyrans, FRR and probably most of all as Magistracy of Canopus.
Fedcom? Psh, they´re just total fanwank author fiat!
My(/our) alternate history(which we even gamed out) is much more fun, where the initial suggestion from Hanse ends up in the hands of Melissa at a BAD BAD timing(early 20s, waaayy too early), which results in a very rude, and accidentally not personally
only delivered, message back, the accidental part becoming a "great insult that must be avenged!", at least according to the troublesome elements in the FS who wants to discredit Hanse and/or stuff themselves with a bit of extra money or assets, or just glory...
Hanse groans in annoyance and "retaliates" by setting up for the war suddenly desired against LC, to be led by the as many of his political opponents as he can manage, while using the worst possible troops for it that he can ever possibly justify.
DC notes that FS will be very busy for the foreseeable future and decides to fix the Rasalhague issue one way or another in the meanwhile(this leads to roughly the same FRR except without the ronin wars, and finishes much faster, LC also gets involved and "donates" a few border planets to get a quick deal out of the event, essentially securing as much of that border as easily as possible).
The FWL also takes not and gleefully starts preparing to hit LC while it´s busy defending against FS. They fail to realise that Hanse knows perfectly well that attacking LC effectively isn´t realistic without going through either DC or FWL as well, and he has chosen FWL to do the honors.
FWL does expect CC to be the ones overrun by FS and prepares their own attack of opportunity in that direction.
FS beginning attack wave basically runs into a brick wall, perfectly in line with what Hanse expected and preferred, wanting to get rid of some idiots and his least loyal troops.
He´s not ready for what is going very haywire.
FWL uses the troops prepared to attack CC along with some other from that area to completely lock down the fights on their planets. Quickly turns into serious meatgrinders way beyond Hanse´s expectations(or anyone´s really, as 2 major well prepared assault forces impacting each other is not the norm) Then...
C* got involved similarly with FRR and helped it go quite smoothly(they really want more divided states after all), and looking at all the fun stuff and even some goodtech that DC managed to squeeze out of the deal(slightly better than canon), mr bigwig chancellor Liao figures out how to get in on the action...
He offers Candace a similar deal as the FRR got, except with the provision that she has to take and hold a certain number of FS planets or the St Ives Compact will be reabsorbed into the CC. With the C* acting as the neutral 3rd party making sure eeveryone has plenty of incentive to stick to the deal.
The FWL slightly panicking sends off orders to cancel the massive attack prepared against LC. A MIM operative intercepts the order, makes it look like it was properly sent, mess up the communications just enough to matter then flees for home with some very valuable information, making a very short stop on Andurien on the way... Oh, she also sent the info to LC.
The FWL attacks into LC do not run into a meatgrinder, worse, much worse, they´re caught before planetfall and more or less captured.
FWL reacts by trying to set up defense against the enemies...
And wow, where DID that Duchy of Andurien suddenly come from? Oh and the CC didn´t bother seriously defending the few planets the FS took, instead they now hit the FWL at the same time the MoC does.
Meanwhile, the TC thinks it´s a great time to mess with FS. On this occasion, surprisingly, they are entirely correct.
Because the DC, now with some neato lostech gear smacks into FS as well.
Supported by C*, Outreach and 5 nearby planets declare indepence during the mess.
FWL scrambles to react to now having effectively 5 enemies facing them from 3 directions, LC uses captured equipment to bolster its troop numbers and launch a limited counter offensive against FWL while just holding ground against FS(who in the area is mostly tied up fighting the best or 2nd best FWL troops)...
FWL forced to a very bad peace with nearly all enemies.
FS, well Hanse mostly did get what he intended, problem is he also got a crapload of landgrabs from TC,DC and SIC, which all together forces FS to a less than great peace, but Hanse uses it to clear out the idiots and disgrace them for pushing such an "obviously stupid war just because a pre-teen girl threw a little temper tantrum" so it´s not a complete loss at least.
Big mess. Timeframe somewhere around 3020 to 3023
End result, a much stronger, slightly larger FRR than canon(+6 planets compared to canon IIRC).
A StIvesCompact which as long as it retains enough planets formerly of the FS, has its independency from CC guaranteed by C*, ending up with 37 planets.
A Duchy of Andurien that is viable(simply because FWL got whacked too much to risk another war with anyone anytime soon) with 26 planets.
A CC that lost 20 planets and gained 93(not entirely sure of the number but hopefully correct), loosing surprisingly little for its gains, and effectively conning C* to give them a nice little tech power up.
A LC who because it was reasonably well prepared, including letting the Dragoons be a primary part of the defense against FS, in the end only lost the planets it freely gave up to FRR to make that border happy, while taking 33 planets along the FWL border.
DC scampered off with 57 planets more, nothing important but improving borders a lot in several cases. The 84 planets for the FRR hurt, but with drastically less issues during the secession, they come out of it much better than canon.
MoC meanwhile took back a bundle of the planet historically affiliated with it, abusing perfect information, chaos and weakness in the FWL to aquire 37 planets.
While TC was taking it cool and easy, just pinching off 13 planets from FS as some payback for old wars onesided the other way.
In short, we end up with a much less monolithic fanwank FS/FC, a DC that is a better big bad antagonist than ever, a CC that can almost be called a fullsized(rather than one-bitesized ) realm and several smaller nations that are suddenly much more interesting and viable to play in strategic games.