My personal opinion is that Klaus Meine is a superior vocalist compared to Anders Fridén and it would be simply wrong to discriminate Klaus, who, in fact, is more qualified for the job. So, ideally it would be like, nostalgic evening with In Flames, Dark Tranquillity and Klaus Meine singing pretty much whatever song he'd feel like, cause he's yet again just superior. Hope you guys back me up on this one. Klaus - da man! And perhaps Boris Becker could have a playstation quiz show between the bands or something. Later Nuclear Blast could hand out beer coasters and Century Media could have like, a canon loaded with glow-in-the-dark condoms with "DT" written on them and if the guy has got a real big one it could say like, the full darktranquillity.com-url on it or something. I don't know.
Or maybe they could record a song together and donate the money to starving people in africa; think big - think Swedish Metal Aid 2.
On a more serious note, I don't see this tour happening. There's just no profitability in it. Especially if you consider that Osmose probably would be a pain. Closest thing to gothenburg metal-retromania would be the 200 000 decibel gig a few years back when Stanne went on stage with in flames and sang gawd knows what. The sound was very poor that night so it really looks better 'on paper' than it was irl. But if you take that and spice it up a bit you could almost say "been there, done that, bought the t-shirt".