Hmmm... interesting. I was under the impression that piloting a fighter was impossible, so my intent was to create "frigate fighters" ("frighters"!) and then use game logic to treat them exactly as fighters -- all of the fighters you aren't piloting yourself would then be converted into wings, with the exception of the first wing which would simply be attached to you as wingmen. Since the "frighters" would count as ships rather than fighters under the CollisionClass, being able to make them immune to friendly-fire would be important (i.e., the CollisionCheckPlugin would check against DamagingProjectiles and Ships and allow the fighter not to collide with the former if it originated from friendly ships, and allow the fighter not to collide with the latter ever).
Of course, this was before I noticed the setCollisionClass() function in CombatEntityAPI... so technically, for "frighters" alone, this wouldn't be necessary. On the other hand, CollisionCheckPlugin would be generally useful enough that it should be evaluated on its own merits.
Incidentally, if they are already flyable, I would lean towards classifying it as a bugfix request rather than a feature request (I mean, I can tell they're obviously disabled for "ship-oriented" gameplay reasons, but at the very least it counts as a "feature fix request"). =)