I think it would be a great idea for all tournaments to do this: Everyone gets a 250 point "side bar" of models that they can switch out of their army before any game they play.
This way you dont' have to always make a static list that is take all comers. Instead you can have some units that are good against MEQ's, but then you can switch those out if you end up in a game against IG.
I personally never use a Demolisher tank because it's only really good against MEQ's and alternatively I would never use an Exterminator because it's only good against non MEQ's. If I could have up to 250 points worth of stuff to switch out, then I would take these tanks and then switch them based upon my opponents.
I dunno, maybe that idea is a bit crazy, but it could be worse.... I could be on crack.