Jump Desktop might be an option, I'm curious too as I'm looking to do the same thing. If I could return my keyboard, mouse, and 4k monitor I'd save about $500 (and barely pay for the pencil and magic keyboard for the ipad). Looks like you could just leave it running and connect when it gets the signal, as in set it up and unplug the display. Could probably have an autostart on startup function too.
Edit: I found someone say screens works better for mac, idk.