There is a problem with the request since you are asking for just about everything that a VTOL can do, but VTOLs are probably the most limited of vehicles. By that I mean they need to be focused upon a particular role, but you are asking for a vtol that does it all.
If you want a gunship you can go with a Yellowjacket, it has a gauss rifle so there isn't a much bigger gun that it could get. If it could then it's going to lose range, which increases it's chances of being knocked out since it is the slowest VTOL i have seen.
If you want the same range as the Yellow jacket, but want speed, then the Hawkmoth is a good option. It has the range, but only half the damage with its light gauss rifle.
There is another higher tech option in the Warrior HX9 that has stealth armor and a very long range HVAC2. BV wise its rather cheap, its fast and has a booster pushing it's speed up to 20MP. The armor is lighter then the others, but if you use it right then its not going to be in the range of most weapons and anything that is in range is going to have a hard time hitting it, with a likely 12 to hit without the vtol even moving. Yes, the HVAC has a chance to blow its self up, but for that range its worth the risk if you can poke at high value vehicles before they get into range of your other units.
But back to your problem, you're better off splitting up the roles and getting different vtols. You can't really gunship and paper cut things to death if you're being blown out of the sky. This means that you need to stay out of the range of as many weapons as possible. That forces a choice between being a gunship and a troop transport since you will need to close with opposing units to drop them off in most cases. For me, a transport needs to be able to move since I'm dropping the infantry on top of the target so that it can perform an anti-mech attack next turn. If you are using infantry in a far less aggressive role and the opposing player has little to no presence in the area you are dropping the infantry then you can still gunship. However, its not something you should count on unless you are willing to forgo using the infantry if there is no big opening on the other players side of the map. Also, keep in mind that your gunship needs tonnage for the gun, armor, engine, and the infantry bay. That is asking a lot from a vehicle that has a 30 ton maximum.
If you are going to use the VTOL for spotting then its best to use one that is not flanking. If you can get away with sitting still then that would be best. The problem you will have is the modifier for spotting while also firing. This reduces the effectiveness of your gunship. Something like a dirt cheap Ferret would perform the role without reducing the gunship's effectiveness. BV and cbill wise it is cheap as can be.
Your request is basically on par with asking for a mech that has the most armor possible, the best ranged weapons, and high mobility. You're better off with a fast transport that is able to focus on getting to the destination while another vtol focuses upon shooting stuff and avoiding return fire. If one is shot down then at last you have the other still going.