It's odd, but the more mobile Naismith in the forward position in our system put Lukaku to shame a few times in 2014. And that's my concern - does Lukaku fit the system consistently, in the way you'd expect from a £20m+ striker (which, in reality, is like a £40m+ signing for our rivals).
Your putting to much focus on the system he would need to fit into, personally I dont think we played to his strengths a lot of the time last season and I would suggest we changed our system to suit.
But thats another discussion for another time.