He is quite flexible with his position so I don't see too many issues. In a 3-4-3 he can play in either of the wing positions. And in a 3-4-1-2 he could play either as the 10 (more as a extra striker/presser rather than a playmaker) or be one of the two up top.
We often talk about needing a back up for Kane. But if Son and Kane are to play as two up top then Son needs a back up as well.