Your description of the Vespid sounds exactly like Stealth Suits are described (except for the saving ammunition thing).
Don't count of them being any more survivable than ordinary Firewarrior though, they rarely survive the first 2 turns in my games (often not even the first).
Imo the Infiltration Cadre fits your overall idea very well and their special rule allows for your flyer to come in very early and more likely. 3 teams of Pathfinder, 2 teams of Stealth Suits and a lone Piranha unit. If any of them get killed (the whole unit) all your reserves come in automatically on the beginning of your next turn....even if it's your first turn if the enemy had the initiative.
As for flyer....Barracuda and Remora are def worth their points and are very cool models as well! So much better than our lame codex flyer both rules and design wise.