Vessels modified for vacuum sealed transfers? Definately a different paradigm than most of us use around here. The only worry I would have would be the pot/seal/lid getting dorked up where it doesn't hold a vacuum any more.
Where would you plan on doing this? Inside? Outside? If outside, would you use 1 burner and move around your HLT/MLT/BK to heat the right one at the right time? If so, you might as well build a makeshift 3-level gravity drain system using ladders, tables, etc. There's a ton of examples of how people have done this. Probably a few in here: http://www.homebrewtalk.com/f51/show...rew-rig-46578/
You could also just use regular ball valves and pickup tubes in your kettles with a march pump and avoid the vaccum thing altogether. $500 isn't necessarily cheap if you're moving to all-grain. A lot of guys do it for much less with coolers and a turkey fryer. Just throwing out options for you to consider.