Turning Raptors into "bombers" does sound somewhat appealing. Damaging a base star is kinda weak though. That's what Weapons Control and Main Batteries are for. And nukes. Making a Raptor on-board airborne and giving it an ability that is already covered by several other means is somewhat redundant.
I do like the overall idea of giving Raptors an on-board purpose though. Here are a some ideas I just came up with:
Make Raptors pilotable and change the text in Command to include unmanned Raptors. If at least one Raptor is present in any space area, all Vipers in that same area gain +1 to their attack rolls. (Yes, against Raiders that doesn't change all that much. But against a base star it doubles the chance of doing damage and it makes blasting Heavy Raiders in space slightly easier. For every Raider icon on cirisis cards, Raiders will attack Raptors if no manned or unmanned Vipers are present. And they will attack manned Raptors before engaging unmanned Raptors, of course. Make Raptors "hittable" at 4-7 (damaged) and 8 (destroyed). With a Repair card you can repair 1 Raptor or 2 Vipers. Maximum Firepower does not do anything for Raptors. But Evasive Maneuvers work on Raptors the same way they work on Vipers.
Especially with the Exodus expansion this may work fairly well.
The downside is, of course, that there are only 4 Raptors. So if you lose too many, you're out of luck for crisis cards, Scouting skill cards and destination cards that call for a Raptor being risked. Tough luck!