“Billy Elliot” has a new boy, 14-year-old Leon Cooke, alternating in the title role from Sept. 19, replacing James Lomas, whose voice has dropped. (That happens.) But offstage, the concerns surrounding the hit British musical are raising the same old question: Will it find a berth on Broadway? Assuming it does, how can they possibly cast it?The difficulty, helmer Stephen Daldry was saying, still “feeling a little bit woozy” after a flight back from New York, is “how you set up structures (so) you can access and train the boys” to perform on Broadway. Does that mean flying Billys over by the planeload from England? Or cultivating Geordie accents among the more precocious students at New York’s High School of Performing Arts? Or maybe scouring the British community in Manhattan in search of youngsters who might — just might — be the real thing? That last point is the crucial one. “The kid has got to be from that place,” producer Jon Finn says. “That’s the whole fun of it.” The financial fun has been “Billy Elliot’s” steadfast commercial grip over an uneasy West End climate that has seen onetime sellouts like “The Producers” going slack. (“Billy” and “Guys and Dolls” were the only big shows not affected by the usual summer softening in London, which was exacerbated this year by July’s terrorist attacks.) The advance is happily lodged in the region of £5 million ($9.1 million) in a 1,527-seater that, says Finn, “on our worst night has maybe five seats free.” What of Daldry when he isn’t working with any of the eight boys now being trained as eventual Billys? The former head of the Royal Court would love to return next year to do a show for its 50th-anni season (“It depends what David and Caryl” — as in Hare and Churchill — “are doing”) and has been in discussion with HBO about filming Churchill’s “A Number,” a 2002 Court success. That venture, in turn, depends upon original cast members Michael Gambon, who can be hard to pin down, and Daniel Craig — “if,” says Daldry, “he isn’t the next James Bond by then.” Separately, Daldry was sounding pleased at the prospect of the Victoria Palace’s neighboring Apollo Victoria next year getting the (unconfirmed) West End bow of “Wicked”: “I like the idea of that theater full of 16-year-old girls.” At least the various Billys won’t have to look too far to find a date. Tribal triumph Productions of “Macbeth” are so common in London (there will have been four major ones this year alone) that a real sensation can slip by. And that is the only way to describe director Max Stafford-Clark‘s African-themed staging of “the Scottish play” for his Out of Joint touring company. As it embarks on an international tour, catch it wherever you can. (The production travels in Britain to Edinburgh and Bury St. Edmunds. Overseas dates include the Czech Republic, the Hague, Mexico and Minneapolis’ Guthrie, as well as two final gigs in the Nigerian cities of Lagos and Abuja in November.) Stafford-Clark is better known for his work in new plays — exactly what Shakespeare’s most compressed tragedy is here bruisingly seen to be. Although the promenade-style staging adds a ritual component to a production rife with voodoo, chanting and gunplay, the director and his team spare nothing in serving up a difficult play from the inside out. Sure, it’s striking to find Raquel Cassidy‘s febrile Lady Macbeth the only white member of an otherwise all-black cast, but Danny Sapani‘s sweet-faced Macbeth gives us both a modern-day African warlord besieged by demons and the timeless agony of a warrior who has more than supped with psychosis. This production invites us to partake in the banquet scene, only to leave us feasting on a genuine fright to go unrevealed here. As for the aftermath of Lady Macduff’s murder, let’s just say I’m shivering still.