Depends on the mode. If commuter rail, probably DT to Clay County but operating it as a hybrid system with more stops and frequent service, similar to the Sprinter in Oceanside (San Diego). If LRT, DT to Southpoint/Town Center as a starter. Given the length, both could be cost prohibitive. If Skyway extension, then Kings Ave to San Marco or the O&M/JRTC area to Five Points via Brooklyn. If strretcar, DT to Five Points/King St. BRT with dedicated lanes is a little more complicated. Ten years ago, I would have said the Arlington Expressway corridor but Regency is dying now. Other interesting corridors would be Main, Kings Rd, etc. The con is our context. We don't have a setting with a ton of existing destinations on a single inner city corridor like Euclid in Cleveland. So your line will end up taking some crazy circuitous route.