I think it ought to be able to tell the arranger that an edit is of a protected style, and THAT file is also protected (keyed to the arranger).
Only problem arises making SMF's of protected styles for songs, but, to be honest, if the styles aren't too expensive, who's going to want to do the prodigious amount of work to FULLY export a style (all chord types, all variations, all multipads, all fills, Ins and Ends, etc.) and laboriously reassemble the style completely to make an unprotected one? If they can buy the style pretty cheaply?
This is what the industry is going to have to deal with. Just like now you CAN get almost any tune for only 99¢ on iTunes, and nearly a billion have been downloaded legally, keyed to their computer (protected), if the styles' price is lowered from where it is now to maybe a buck or so, nobody will bother. But EVERYONE that uses the style WILL have payed a dollar. I would not be surprised that for every legal style sold at the moment, it gets copied at LEAST twenty times, so if everybody BOUGHT it at a dollar, they'd make TWICE what they are now (conservatively).
But keep them at $10-15 bucks or more like they are now, and MAYBE someone would think cracking it worth the work...
iTunes has shown that, if the price is low enough, people WILL pay for protected content. And a billion dollars is back in the hands of the industry, rather than being lost to piracy. The inference is obvious. Protected styles WILL work, and work well, as long as the prices are kept low.
Steve Demming... you reading this?!