In theory you're correct. However, having done a few times in real life, it's not a practical issue. So go for it.One cautionary note - unless you're spot-micing the cymbals (and even then, to an extent), then the electronic kit is going to bleed into your overheads, so you'll hear two things with each, say, tom or kick hit - the very dead, flat sound of the beater or stick on the electronic pad, and then the sound of the sample. Additionally, if there's any latency between the two it could potentially sound a bit funky.
As for the OH mics... how cheap is cheap?