I don't really see an issue if they are just plain better than standard fighters. They need to be - they cost you your pick.
I don't bother building fighters (except for numbers when maxxing out fleets) whenever I pick a fighter type class - say raiders, raptors or planes...
You shouldn't compare them to normal fighters; you should compare them to the other possible picks.
Raiders, Raptors, and Planes may all be better than fighters in many situations, but they aren't ~strictly~ better than fighters. That is, you can theorize situations where fighters would be more useful (planes have extremely low health, so if you are against a fortified position with tachyons and need to create a lasting battle, fighters might be a better choice).
Currently, however, bulletproofs are the only special to 100% obsolete a core triangle ship. There is no situation where you would rather deploy fighters than bulletproofs, which I would argue is a bad thing (There are of course many situations where you would want to deploy fighters AND bulletproofs, but that is not my point). I would also argue that having a bonus ship that is just core triangle ship + special ability sets a bad precedent as far as making bonus ships unique and interesting goes.
A higher material cost than fighters would be enough to allay my balance concerns; from the "unique and interesting" side of things I think their stats could perhaps be tweaked a bit, just so that it's not obvious to anybody who compares the two in the shipyard that they are carbon copies of each other.