Yeah yeah, y'all can be sure that around that gig, there'd be no shortage of merchandise. I'd have photographers and video artists there, fashion designers too - here in Berlin, everybody's willing to join any sort of music/arts/whatever project for a beer or two!
But all that fun & vanity stuff aside - I mean it when I say that this can only be huge fun if everybody involved shows some commitment that goes beyond the beer-drinking and t-shirt-wearing part. Me, I've been known to get pretty mean when during a rehearsal session I discover that somebody in the band hasn't prepared his part and puts dumb questions like, "This song is in the key of A, isn't it? And it's that slow song where the bridge comes after the second chorus, right?"
As I said, it's easy and inexpensive to provide infrastructure over here. But without an honest working musician's attitude, the whole shindig won't play out!
With regards to the timing - naturally, it would be very great to have the SWW people there. But April is half a YEAR away still... Why not do it in the first week of December and then, if it's a success, again in April? First week of December has another advantage. I've heard that, for reasons I don't entirely understand, you fellers out there are quite fond of German Weihnachtsmärkte (Christmas Markets), and early December is when the entire city is full of them. So anyone interested might even bring the family for a long weekend - as long as Daddy has permission to get drunk on beer and loud music while Mom takes the kids for a ride

Taking that into account, maybe Michelle and the SWW gang would like to do themselves a favour and come over already in December, too?