South Florida impresario and veteran Broadway producer Zev Buffman foresees a future for stage theater — in radio. Not just for any theater, but orphans like the Parker Playhouse that are too big for local theater troupes and too small for Broadway tours. And he wants to do it in part by reviving the genre of mystery/thriller plays. Local audiences will see his first foray this month with his production of Agatha Christie’s The BBC Murders, four radio plays lost for a half-century, uncovered by Buffman’s detective work and adapted by grafting full-fledged theater techniques onto a vintage radio drama foundation.