AP Rakan?
Full AP
good or nah?
Full AP
good or nah?
yes
I have a 80% WR and I play rakan AP or AP bruiser. Legit what I do is rush Ardents and get spell thiefs as my starting item. If you mean for mid... hes not good. Too low range and mediocre wave clear, with no way to duel reliably bc hes so low range. Go Aery on him and get gathering storm. Its so good.
I played him in jungle ap/hybrid AS, something like azir (Nashor's tooth....) and it works really fine
Fun? Yes. Good? Not currently, but there is a change on PBE giving him 30% AP additional damage (20% on his w, 10% on his Q) so it might become a thing if these goes live.
Rakan does not really do damage. AP Raken scaling is bad and cooldowns are too long. The only way to actually do damage is :

He is 'ranged' so rapid fire cannon works. Fleet footwork is the rune you should use.