How do you brew with only two vessels? Where do you hold your sparge water? If you hold it in your kettle, how do you collect your wort?
I do a Hockkurz mash and don't sparge. So I heat the water for the infusions in the kettle and then gravity drain to the mash tun. When the mash is done, I either put the kettle on the floor and use gravity to do a manual vorlauf and transfer (which then requires lifting the kettle back up to the burner) or I hook up a pump and use that to vorlauf and transfer.
I have two additional kettles from previous incarnations of my setup, so I can add an extra vessel and sparge if I want to, but I don't really see the point anymore.
I can see the advantage of all-in-one systems for people who have to setup and break down their gear every time they brew. I used to have to drag my gear up from my basement to my kitchen (mashing and lautering) and my garage (boiling). Having to setup everything and then put it away was drag.
That's the situation I'm in now. I could install a utility sink in the garage and get a Grainfather or something similar, but I'm fine with things as they are for the time being.
I understand that the SS Brewtech mash tun is over 30lbs empty. I would hate to have to hump that out to my compost pile with 12lbs of grain and 12lbs of water.
Since it's sitting right here, I just weighed it and it's 32.2 lbs. empty (including the lid). I use a filter bag in the mash, so I scoop about half of the spent grains into a trash bag lined bucket and then upend the bag into it. I do feel bad about throwing spent grains into the trash though. Now that we've got a decent sized property, I should look into composting.