Here's an idea I had a few year ago when considering the vulnerability of traditional gunships to modern AA weapons and the consequent desire for greater stand-off:
The Vertical Gunship.
This is a converted transport plane similar to a classical gunship, but the difference is that it only has one high-velocity gun, mounted to fire downwards at the centre of gravity, in a limited-traverse mounting. The aircraft has a large optical sensor turret on it's nose, similar to the usual EO turrets but much larger and with greater magnification, and a control room with a operators and a ballistics computer. With all the volume available in a transport type, you should be able to design a system that lets the gun have a long barrel that retracts or swings out of the way for landing. My default mental picture is of a ball turret in the floor through which the gun barrel can slide. The hydraulic rig that moves the breech around can slide backward in the airframe, thus giving it more room to retract the barrel completely inboard for landing.
The modus operandi is that the the aircraft stays at about 15,000ft, well out of the envelope of MANPADS and portable AAA. When it finds a target, it flies towards it, and the ballistics computer, which also takes inputs from the aircraft flight control system, computes the correct moment to fire the gun. The ammunition has LED tracer in it, which is picked up by a second EO sensor mounted near the gun, and tracked to correct subsequent bursts (effectively a passive version of the closed-loop spotting used by Phalanx).
Why not just drop a bomb? Because a high-velocity cannon shell will be much less susceptible to wind drift and therefore more accurate.
Okay, so why not drop a guided bomb/missile? Because they're disproportionately large and expensive for small/low value targets. The aircraft can also carry way more shells than anybody can afford missiles.
