I can actually see the player flying capital ships more than I can see them flying corvettes. Frigates, in paticular, are perfect. The Firelance and Vengeance class frigates are both perfect, because they have fixed-firing weapons that are powerful. On the Firelance you'd be using the Ion Beam, and in the vengeance you'd be using the fixed plasma bombs. Corvettes, on the other hand, have all of their turrets rotating, and that won't really be usable. You might be able to fly them, as only the pilot, since they normally have crews of 3. It'd be boring, though.
Actually, the Kushan Revelation class destroyer has rotating ion beams, which gives it an edge in destroyer combat. The obvious counter is that the Skaal-Tel has double-barreled mass drivers, so while the Skaal-Tel is more adaptable overall, the Revelation has an accuracy edge in capital ship combat.
As far as balance goes, the player will get promoted to bigger and bigger ships the whole game, to maintain scale. By the end mission, you'll be flying (and at that point, have to fly) Firelances or Vengeances. The Demo release will be fighter-only, though. Dogfighting is going to be very, very tense and exiting because there will be a lot more ships then you see in Freespace, in general.
Also, there is a giant balance change from Freespace that I'd like to now bring up. In freespace, bombers are VERY slow and VERY armored, and rape capital ships. In homeworld, they're pretty speedy (150m/s, interceptor is 165, scout is 200) and they're the most fragile strike craft. This balances the ship out, in a way. You just can't ever beat dedicated strike craft in a bomber. Also, plasma bombs require, in the canon fiction, to shunt drive plasma from the engines. Therefore, part of flying a bomber is energy management; you give engines your all when approaching, then bring gun energy back to fire bombs. You can only fire two shots before you have to recharge (from 0%). Recharging takes from two seconds at max energy to more like twenty seconds at little energy. Your speed also decreases a lot. I can see the defender being abused pretty heavily, though, as three rotating turrets can be pretty fun.