I think once you have wound a few sets of single coils the answer to this question will become clear.
A humbucker is not just two single coils stacked side by side. If you take two fender single coils and try to make them into a humbucker they won't fit properly and you will potentially have polarity and wiring problems. A single is bigger than half a humbucker and both singles will have magnets that have to be correctly alligned in order to acheive hum cancelling.
In a humbucker both coils are usually identical (in terms of DC resistance, number of turns, wire gauge, etc.) however if you just take two single coils it is very unlikely that they will be identical (bridge, middle and neck singles usually have a different number of turns) so even if you did get it assembled and wired it wouldn't be totally hum cancelling.
As I've said before wind a single coil pickup first - you will be surprised how difficult it is to get a decent result. Once you can wind a competent single coil try something a bit more ambitous.
There is nothing wrong will coming up with new ideas but I think you might be trying to run before you walk.
Good luck.