Agreed. In fact, the engine bay wiring harness can probably be kept mostly or completely intact. If the stock sensors are being reused, there's no need to mess with the wiring harness at the sensor end. If the position of components in the engine bay is not significantly changing, then the routing of the wiring harness doesn't need to change either. At most, you're going to have to figure out how to connect the harness to this new computer, which can possibly be done without having to modify the stock ECU connector. I have seen adapter harnesses before.
Oh OK. You are correct it seems to support most CKP and CMP designs. So most of the work is actually just getting the pin out and putting those in the speeduino board... I may have to give this a shot then. Not sure about ignition wiring but when I get some time after work I'll read up on how thats handled.