The century-old Merriam Theater, which the Kimmel Center acquired last fall, has a handsome old interior – as well as painfully cramped seats (which some patrons have to walk through offices to reach), poor acoustics, outdated sound and light equipment, and dressing rooms that literally used to be stables. The new plan is for the Kimmel to partner with a developer to tear down the seven-story building currently housing the Merriam and completely revamp the place (saving the auditorium’s architectural details) while building a skyscraper above it.