On the AHA big brew day I was talking to a couple of guys that walked up that fix and clean kegs.
In a nut shell they said they use high pressure and a "mold" to force the keg back into shape. It sounded incredibly dangerous to me but that is what they said.
I agree on the HLT or BK idea. Mainly the HLT and here is why, MOST Euro kegs are not 15 gallons. This means that as an MLT you would only get slightly more space than a 10 gallon Rubbermaid cooler. using it as a BK has the same issue of limiting how much can be boiled (I love my 15 gallon BK because I can boil and retrieve 13 gallons with ease for a "double batch".)
You can also use the cut top as a false bottom. For the life of me I can find the thread but you can drill a bunch of small holes (What I did) or grind slits into it. Then use a rubber/silicon carboy bung and slide that over your dip tube. Here are some pics of mine. I have used it for over a year, and direct fired the MLT with great success.
Hope this helps and GL!