[Edit August 24: 55000 (the estimated number of 'Mechs in 3025) multiplied by 4/3rds is 73300, a mere rounding error away from my count for 20YU. Per 20YU, the War of 3039 petered out into the usual pattern of raid and reprisal, so attrition should be back in equilibrium with production, which means 'Mech production by 3050 should likewise be 4/3rds of what it was in 3025. (I.e., up to 3600/yr from the old 2700/yr.) The ComGuard was deploying during this period and supplying 'Mechs to other forces, however, which would account for some of the increase.
AFFC 268 Regiments, 1 Battalions [sic] DCMS 99 Regiments [including Ghost Regiments] FRRK 16 Regiments, 2 Battalions FWLM 72 Regiments, 2 Battalions CCAF 30 Regiments [some are short a battalion] CG 50+ [sic] Regiments TDF 14 Regiments MAF 12 Regiments, 1 Battalion OAMC 3 Regiments [full regiments now, unlike 3025] bandit [8 Regiments and 4 Battalions]
When the Clans invade they destroy many regiments and capture several factories. Per TR:3050, the Successor States step up production at their remaining facilities. That wouldn't have recouped all their losses, but for the sake of estimating production, suppose we round the Inner Sphere up to 79000 'Mechs (a thousand for each non-Clan enty TR:3050). Subtracting the ComGuard's 50 regiments would leave 72600, or 1.32x as many 'Mechs as were going around in 3025.
I notice that MW2e has 1.33x as much chance as MW1e did of a "Successor State" character scoring a state affiliation (almost 36/36 instead of 27/36). This implies that the Successor States were building 3600/yr shortly after Tukayyid, and agrees with the figure above derived from TR:3050. /Edit]
If the "Successor State" table represents 3600 'Mechs/year:
