Curious if you ended up going forward with your project? I would also like to drive an induction motor from an arduino and I am currently doing so using the analog input of a VDF. I thought about using a MC3PAC and writing code to drive of as well, but a native solution would be better. Surelly the MEGA would be able to do it.
As you I also get frustrated with people that know it all and point the obvious when they clearly have no idea what is being asked. Oh well...