Remap holding ALT at startup?

[Andy]

Is there a way to change the hotkey to switch between booting windows and mac at startup?

[zarmanto]

I doubt it. That's declared in the firmware, and I don't think it's user configurable, any-more-so then the BIOS hotkey is configurable on standard PCs.

(Aside from that: Apple has used the option/alt key to access their startup manager for nearly a decade... I don't think it would make much sense for them to start letting users change it now.)