Nice fic, the plot is a little overused but it never gets old.
As for the poll why don't you put powerfull witches to choose beside the girls already? After all, he gets the magic from them so they'll have to be powerfull. In the harem I'd like to see a profesor (Sinistra o Vector I suppose).
Also if he bonds something like say a vampie or a veela does he gets abilities or something?
Anyway do wathever you like I'm enjoying it so far.
-Kuro-