Templates
I've run campaigns where I handed out templates and expected everyone to select one. A few points were left unspent, as to allow a few tweaks here nd there in skill points and ability scores, but that's it.
I don't like the idea of a party composed of four classes/races picked willy nilly from the PHB. It strains my suspension of disbelief a little too much. Like your example, I've said, "We'll be playing a military style campaign. Your characters are part of a holy order of knights, a few of humanity's last defenders. Before your outpost lays a blasted wasteland where the armies of Necromancer Lords mass. Brace for impact."
Well, it wasn't quite that dramatic, but everyone was expected to play a martial, non-spellcasting human - fighter, fighter, or...fighter. The focus was tight, the characters were cohesive and those who showed up to play knew what they were getting into. Anyone who didn't like it didn't have to play.
All I'm saying is that you, the DM, have the right to dictate the terms of the game. Since few are willing to sit in the Big Chair (although you prefer to stand, heh), I think the DM really can have his say. This isn't proclaiming that PCs are pawns in your screenplay, but as my friend Lyonel once told us, "I have a story I'd like to tell and I'm wondering if you guys would like to play the following roles." Presented like that, it was easy to say yes.
I think its also important to note that a "scripted" campaign doesn't have to last a long, long time. Some stories take less time to tell than to others. That can also be conveyed to the party during char creation. "I'd like to run an all rogue campaign. The goal of the game is for your characters to rise from poor street urchins to guild lieutenants. I think we'll need about 20 sessions to pull it off."