Could a PV powered water vapor Arcjet do Asteroid to LEO and return?
Applying the KISS principle here - Keep It Simple, Stupid.
I see asteroid minerals as the best near term economic opportunity in space - most other things will be harder - and expect the ability to do Asteroid to LEO and return transport with fuel/reaction mass produced at the asteroid to be a threshold pre-condition for success.
Water based Arcjets seem to embody simplicity with potential for low rocket dry mass and it offers what may be the easiest to find and produce and store in-situ reaction mass (water) as well as potential for high rocket durability but I don't know the limits, i.e. can an hypothetical rocket manage its own mass for such a round trip and carry some payload as well? (And do it over and over!)
Rather than look to asteroids in the Asteroid Belt I would look to Near Earth ones for the lower delta-V between asteroid to LEO and for the abundance of solar energy.
Rather than metallic asteroids, I would target carbonaceous ones, for the water content as reaction mass and for chemical feedstocks for any refinery. Carbonaceous materials are relatively soft and should still contain nickel-iron (where the high value Platinum Group Metals as well as Cobalt and of course Iron and Nickel are found) as grains and nodules.
Bennu seems a suitable example.