I was planning on using weldless bulkheads, easier for me to maintain myself. Where I work we have all sorts of welding/cutting tools and they work with stainless a lot, so I'm not real concerned with cutting the top, (plasma cutter... cool) but I'm gonna seriously consider the weldless bulkheads 'cause if you mess up welding stainless, you'll get rust.
I plan on three burners, I'm building my own version of the brew-tree / MoreBeer sculptures, and want to get as close to the "real thing" as possible. I may go to a cooler convert for awhile before using the burner, not even sure I need the burner on the mash tun, if what ever I use is insulated, I should only loose a degree or two, so it's most likely not needed, unless I do a step infusion. I dunno, the option would be nice to have, even if I never use it.