Ya I ran into that problem on the way. I figured you could set a "power on" timer and also in terminal set it to power on after power failure. But both of those aren't ideal.
This is what I ended up doing: I removed the power button, removed the plastic lift frame under it, cut out the rubber nipple under than and clipped the black plastic "frame" it was connected to. This gave me access to the actual button activator. It is two leads each with its own pad. When the button is pressed the pads touch, activating the button. The pads are laminated in a tough plastic sheet. I clipped the plastic sheet away from the black plastic "frame", then trimmed the top of the plastic until I was close to the pads. Then I got a razor and separated the plastic laminate to release the plys. Now I can pull the pads away from each other and the power button isn't activated anymore. I discarded the trimmed off pieces and the rubber nipple. Then I got a thin piece of cardboard paper to slide between the pads. Then put the plastic lift frame back and connected it back to the metal hooks. Then popped the power button back on. Problem solved! The machine no longer turns off AND if I do need to use the power button then it's as easy as popping the power button off and sliding the piece of cardboard paper out to activate the power button and then putting it back. Not as great as a perfectly functioning power key but it beats a lot of the other options.