ZDoom

Well, to just do something like that wouldn't actually be that hard anyway. The tricky part is making nearby actors go to the next level with you. But even a limited player-only version would still make level transitions that much smoother. Though something tells me you probably can already do that with ACS somehow, and somewhere someone already did it.

This would actually be a good idea. Kinda opens up possibilities for things like changing levels on a moving elevator or even a moving platform in general. I second this one

While everyone is making insane feature requests, here is mine. Remember Half-Life? Whenever you changed levels most everything nearby changed levels with you. Same idea here. Can it be done? [i]Should[/i] it be done? I have no idea. Obviously it would have to be handled very very carefully, especially if the actors retain their tid and special after the "teleport". Yes it is probably more trouble then it's worth, but that's my insane feature request, and I am sticking to it!