I don't understand why "the base would have to be underground" is such a deal-breaker for so many people. I mean it would suck if your whole environment is like a typical basement, but these could be quite large living spaces, well lit with plants and trees and big empty spaces. Lava tubes on Earth that are spacious and miles long aren't all that rare, and on Mars I think the expectation is that lower gravity should tend to result in larger lava tubes.

The perchlorates are a problem, but not one that's impossible to deal with. One possible workaround is to have space suits that you never actually bring inside, you just sort of climb in and out through a hatch in the back that docks with the habitat. Similarly with vehicles, they could dock with the habitat so you can get in and out without going outside.