Hmm, I may shelve the idea then in favour of something a little more conventional, thanks for the help!

I know brushless motors aren't the biggest fans of being linked together, which is why I mentioned about the (smooth)belts to a drive shaft, allowing each motor to spin at its own rate I guess in theory. In practise though it's probably just going to be a whole lot of work to not as much gain from the sounds of it. Probably work out cheaper by the time I've done with the inevitable failures and replacements haha