With these smaller ships there is no need to worry about artificial gravity. 2300AD canon ships like the Thorez (200 dTon) [pgs. 228-230, 2300AD] make no use of artificial gravity. In the game's rules you just get a lower crew comfort rating, while in the setting universe I'd assume there would be exercise equipment on board and pharmaceuticals to prevent bone and muscle loss. Perhaps they'd even have DNA modifications similar to the Micro-G Space Adaptation [pg. 125, 2300AD].
To convert to 2300AD the weapons and FTL drive will need to be switched as previously mentioned. Also some reduction of the on board fuel may be needed as the 2300AD stutterwarp drive only requires power, not hydrogen. It may be possible to swap out the jump drive and drive fuel directly for a stutterwarp drive and an improved power plant. Those vessels with the ability to land and take off from a planet will need to retain enough fuel to do this.
I'll try to convert the first three and see what happens, but I'm not too familiar with the Mongoose system yet. If it turns out I'll post something. My comment was more in relation to upcoming products and their usefulness to me and other 2300AD fans.
Benjamin