For me, removing mirrors is not an option. My driving is mostly urban, including plenty of parking lots. So in addition to watching out for vehicles, I also have to watch out for pedestrians who will brazenly step into your path and dare you to hit them (so they can sue you).
Replacing a mirror with a camera might work, but that may be more time/effort/cost than I care for. I'm mainly looking for cheap easy stuff that will have a measurable effect.
I already have a "real" project car (an older BMW). So the stuff I'm doing with the Prius is just a few minutes here and there, when I have some free time. Actually, pretty soon I'll be launching into a complete suspension overhaul of the BMW. So I may not have time to tinker with the Prius for awhile.