What I did was position the power button right under the grille. A small button was use on top of the grille to reach and push the power button to turn the MacBook on.
I've research on other way of power on the MacBook, ended up with nothing. Since the newer Mac kill the soft power-on feature, we have to find a way to reach the power button. Older PPC Mac can be power on by pressing the power button found on old Apple Keyboard.
Oh wow, that is clever! I assume you have tried one of the old USB Keyboards just in case? We have a few at work I could try with some of our MacBooks there..
I have a MacBook I purchased as a write off really cheaply, for the screen, as it had white wine spilled over the keyboard, followed by the computer stopping working (who would have thought!). However, I cleaned off the logic board, left if for a while, and now it works, except the top case and optical drive.
I don't need a MacBook (I already have a MacBook Pro, and my soon to be wife has a 12 inch iBook G4 and doesn't want to upgrade), and I couldn't sell it in good faith, given its history, so I'm using it in a Mod, but again, because of the history, I don't want to spend too much on it, and a new keyboard/top case will be about $75 from eBay, which is a lot just for a power switch