And here's my take on the naval forces available during this time. The numbers are based on what we know the Clans have, plus information from Klondike and Wars of Reaving about what other ships they took out of the caches (or were destroyed). I have inflated the numbers in certain classes in order to match the canon number of 401 ships (402 if you count the McKenna's Pride which is blown apart in this AU). Tell me if the numbers look right, please.
First of all: here are the numbers of WarShips that ComStar/WoB had access to after the Exodus (does not include any ships they produced in the interim).
ComStar/WoB: 1 x Bonaventure; 6 x Vincent; 3 x Baron; 1 x Carson; 4 x Naga; 1 x Riga (York); 11 x Essex; 8 x Lola III; 1 x Quixote; 5 x Aegis; 2 x Congress; 3 x Sovetskii Soyuz; 3 x Black Lion; 1 x Cameron; 1 x Potemkin; 1 x McKenna; 2 x Newgrange
Total: 54
Next are my take on the ships that would have gone on the Exodus, with notes where necessary:
Exodus: 4 x Bug Eyes; 6 x Mako; 36 x Carrack; 38 x Vincent; 7 x Samarkand II; 4 x Baron; 1 x Concordat; 1 x Davion I; 8 x Whirlwind; 22 x Riga (York); 16 x Essex; 39 x Lola III (Note #1); 1 x Wagon Wheel; 11 x Quixote (Voga); 1 x Winchester; 38 x Aegis; 24 x Congress; 5 x Kimagure; 12 x Black Lion; 40 x Sovetskii Soyuz (Note #2); 7 x Avatar (Liberator); 12 x Cameron; 1 x Du Shi Wang; 2 x Monsoon (Note #3); 32 x Potemkin (Note #4); 8 x Texas (Note #5); 17 x McKenna (Note #6); 8 x Newgrange (Note #7)
Total: 401 (I added some Makos (4), Carracks (7), Vincents (14), Samarkands (4), Barons (3), a Concordat (1), a Wagon Wheel (1), a Winchester (1), and Congresses (7) as 'filler' to reach the 401 mark. I decided on the three Taurian ships as having been in mothballs all these years, activated in the aftermath of the decision to launch Exodus.)
Note 1: We are told that the Lola III is the second most common vessel of the Exodus Fleet. But not according to the numbers I have crunched here. I added one more Lola III to make it the second most common vessel (40 Sovetski Soyuz, 39 Lola III, 38 Aegis).
Note 2: We are told that 'about forty' Sovetskii Soyuz survived to depart with the SLDF on the Exodus; I can only account for 17, however. I find it surprising that there would be 23 of these ships in naval caches, but . . . perhaps it is so.
Note 3: We discover in Liberation of Terra, that Kerensky added two Kurita battleships to his Fleet. No class was specified. I have assigned them as Monsoon-class; older ships that are no threat to the SLDF.
Note 4: Likewise, we are told that only 30 Potemkins survived--and that one of those was lost. My numbers show 31 on active duty in Clans and one more that was lost (Clan Widowmaker Ship Egg Sack).
Note 5: Just seven Texas-class were part of the Exodus; the only seven to survive the conflict. TRO 3057 even mentions that two of the survivors were then subsequently destroyed! But that doesn't match up with what is listed in succeeding books: there are 8 Texas class ships, and I cannot find a note indicating the loss of any Texas prior to the Wars of Reaving. Seven ships are on active duty, the Prinz Eugen serves as a penal ship, and another vessel (Perth) is mentioned as having surrendered in Klondike. Now, Perth could be one of the Texas-class belonging to the other Clans, just renamed. It isn't clear. But that still leaves 8. Not seven, and definately not five.
Note 6: Twenty-nine McKenna-class survived the Amaris Coup and the Liberation. Eleven of those were scuttled (but it seems like that one of those was actually repaired by ComStar/WoB). That means eighteen departed on the Exodus. I can only account for 9, though. I have decreased this by one, since this scenario requires that McKenna's Pride gets clobbered on the approach to Earth.
Note 7: We don't know how many Newgrange-class ships were in the Exodus Fleet, but I have given the number as 8. These are rear-area ships, but they will still have suffered greatly from Amaris raiders. And the presence of them gives an explanation for how the Clans developed their space industry so quickly.