Is Flesheater Nasus going to be a thing?

It could be; the extra lifesteal and AD early is nice, and if you still just Q farm to last hit that's still 1.2-1.4 AD a minion wave (1.4 for Cannons). Since you get the AD just for using it, not necessarily killing, you should be able to use it before a Q (or auto Q).

infinite ad, infinite hp. The longer the game lasts, the quicker you will stack it thanks to minion hp increasing as the game goes on

So it's basically old ?