AA etc. are for smoothing edges of 3D objects, not to upscalling screen like mentioned FSR. They are not related to each other.
So this feature would help only for 4K and eventually 1080p users (most of PS3 games rendering in 720p or even below). Honestly I doubt it is enough power for that on RSX side. Lanchos and similar algos are quite demanding.
What could be possible is upscalling by Nearest Neighbour, it is cheap and should brings results similar to native 720p experience. Such plugin exist for PSTV for both native and PSP virtualised environment and greatly increasing video quality. It is called Sharpening.
I have bring such idea few years ago for PSX and PS2 emulators but no one care. ;] Maybe bounty could change that.