There already exists several files which can convert specific unidirectional brushless ESCs to bidirectional ones (such as that for the TZ85A, sadly discontinued). I've been playing with a file from the SimonK series for my Red Brick 100A V2 ESCs for a potential Featherweight to convert that to be bidirectional but it requires some fiddling in assembly source code, compiling it and then flashing it to the ESC to see if it works with no guarentee that it'll "work".

I am sure I found a page at one stage detailing how this works - if I get back onto my laptop in the near future, I'll see if I can find the page I am thinking of.