I'm in the same boat. My daily driver is a 2008 Macbook that I added another 2gb of ram and a SSD to - works great! I highly recommend opening it up and cleaning out the fan if you haven't, that made a huge difference in how often the fan spins up.
Great idea! I've messed around with things like this in the past, though I've used my pedals for music editing and DJ software. I opened sourced my last attempt, which includes a neat little python GUI to reprogram the keys (https://www.manykey.org/).
Haven't tried foot keys with an editor, but it seems like once you integrated them into your workflow they would be quite useful.