This would be so unbelievably awesome! The Freespace series was pretty much the last of its kind, back when space shooters were everywhere. It was absolutely amazing. It's funny though, since the Freespace engine is now fully public domain, it serves as the base for many mods (most notable one recently is probably Beyond the Red Line {nBSG}), and I'd actually find it entertaining to play a Sins mod in the Freespace engine
Seriously, the capital to capital battles were epic, and I too was immediately reminded of Freespace's beams in this game (I mostly play Advent). The only major differences would be the emphasis and variety of strike craft, which were exclusive to capital ships and could individually jump themselves (Freespace DID play from the lil flyboy's perspective, after all), and the lack of dedicated long range frigates. I suppose the closest thing would be Illuminator-esque beam corvettes like the Rakshasa and Sobek (although I feel the equivalent Deimos was more of a brawler). They might fit the heavy cruiser role better here... Maybe beam updated light cruisers would be more accurate for the LRM role. Really, I guess the parallels aren't necessary. Freespace had its own fleet composition, which seems balanced and flexible enough to work well in a strategy game.
Coming from someone who is completely computer illiterate beyond playing games, I'm not sure how valuable my suggestions are, but I'm just throwing up ideas.
I read somewhere that capital ships can have only 6 abilities or something like that. Does this apply to its "build strike craft" buttons? Would it be possible to add more types? Would it be possible to change those types as the cap ship leveled up?
I think the best layout for strike craft would be the following, if possible. There would be only two capital ships for each faction (the destroyers, Typhoon/Hathesput, Demon/Ravana, Orion/Hecate, maybe the Iceni for the pirates/NTF?), and the super weapon would be replaced with the super ships for the Shivans and Terrans (Lucifer/Sathanas, Colossus). Each capship should have the ability to contruct 6 different ships, or possibly reduced to 3 spread among the different capships (although this makes less sense Freespace wise). So is it possible to change normal abilities into produce strike craft abilities? You would need each of your basic strike craft archetypes in Freespace, the interceptor, space superiority, heavy/fighter-bomber, light bomber, heavy bomber, recon. From there, I think that the type of each archetype you build is based on your capship's level, determining which technological level of strike craft you can build. ie, level 1-3 Apollo, level 4-6 Ulysses, lvl 7-10 Myrmidon for the superiority fighters.
Strike craft would need to be given the ability to jump, and serve as the primary harraser/recon unit without its host being in system. More nebulas/storms need to be present, and the AWACS ships are needed to see in there (they should be very tactically significant locations, expecially regarding the Shivans. Nebulas are also the primary resource locations (it's a gas in Freespace) which has to be harvested with collection/refinery ships. Metal can work like it does now, but I guess you would replace crystal with gas? Perhaps a neat little thing for AWACS, you could have AI ALWAYS be on combat auto-pilot, unless you had an AWACS, and you could only micromanage strike craft within AWACS range.
Lastly, since the Shivans are not thoroughly described at all, some assumptions/adaptations have to be made. They would not colonize, all of their infrastructure should be orbital or ship based. I'm not sure how this would work in Sins.
Ramble ramble. I have no idea if this is technically feasible or not, but oh man, it would be sooooo awesome!
