When Dick Scanlan files his taxes, under Occupation, does he put “Richard Morris rewriter”? Morris, a middling mid-century scribe, penned the screenplay for Thoroughly Modern Millie, revised successfully for Broadway by Scanlan in 2002. Now Scanlan has “revitalized,” as the marketing for it goes, The Unsinkable Molly Brown, a 1960 Broadway hit, with a book by Morris, that was Meredith Willson’s follow-up to The Music Man. Scanlan’s Millie, to these eyes at least, was a sloppy rehash of an awkward premise that didn’t know exactly what it wanted to be. (You can judge for yourself when Encores! encores it in May.) But on Willson’s Molly, it turns out, Scanlan has done a bang-up job.