If an APU can provide significant thrust to increase take off performance, then it would sure as hell be able to provide the thrust to taxi a heavy a/c on the ground, and retain all the benefits of a standard apu, without increasing the aircrafts weight. Would this not be a more logical solution?
Not correct! Getting a little bit of increase in MTOW due a few lb extra forward thrust does not at all mean that there is enough thrust from an APU to bring 250 tons from a standstill to movement!!
When it comes to eletrical motors on the nosegear- well most likely not usable on wet or slippary taxi ways (which it is half the time in northern Europe at least)!
Sounds like a waist of $ to me!