I am also considering making my own H-bridge. I have seen that it might be a challenge, but I am interested in learning electrical engineering, I am up for a challenge, and I might be able to have a heftier motor controller.
Apparently MOSFETs can be paralleled and share a load, so you may be able to do the same with H-bridges using MOAFETs. Below is a discussion concerning DIY H-bridges that might be of interest (aka, not as easy as one might expect).