my 4x12 is not an amp, so im cool with that. i'm fine with having my amp off stage - prolly would just need a longer speaker cable but that is doable.
seriously though, no amps on stage is not very rock and roll but whatever floats your boat. i can see where they are coming from maybe with stage volume, volume wars, etc. but my experience with a modeller through a monitor sounds like garbage. would you still plan use an amp but just have it offstage?