And they would still be superpowered.
Yes, and no. Sure they would have enhanced powers but a more grounded explanation for them than some of the ones that some DC characters have. Plus I could see them not being too overdone, too overpowered, and their 'costumes' wouldn't be so fanciful. If they had costumes at all.
You wouldn't see aliens, magical, or non-human looking characters, like Killer Croc for example. Though you might get a Killer Croc who resembled Vinnie Jones's Scales from the Cape TV show.
But perhaps a cyborg character like Metallo or Reactron, I could see Arrow pulling that off. Minus the kryptonite hearts. I could see the show using medical experimentation as an excuse for 'super' powers, something to take it out of the realm of the fanciful.
DC also has a lot of characters who don't have superpowers but advanced technology, like Firefly (which is already coming to the show), so I could see them using more guys like that before they went to superpowered route.