got a free water heater

While it's the right shape, the metal is way too thin for your purpose.

i was thinking of putting a thicker plate on the lower edge, as i sorta agree with you.
of coursei'll have to cut it up first to asses how thin it actually is

It's actually rather thin since it's, effectively, little more than a tall stock pot used for heating water.
Have you ever noticed just how thin the average SS/Al stock pot is?

I built one like that years ago. Metal is fairly thin so it will need some bracing. You will probably want about 4 cresant moon shaped pieces of 1/8" plate for stiffeners as well as an angle iron lower edge. Add a replaceable scraper edge, preferably with a couple passes of hardsurfacing bead on the cutting surface.
Most tanks are lined with a glass/porcelon finish. It makes cutting it with a OA torch quite fun but it does cut nicely with a saber saw and suitable metal cutting blade. Wear ear muffs, it's noisy. I suspect an abrasive blade in a 7-1/4" circular saw would work, the metal is a bit thicker than the abrasive blade likes.
Tater wrote:

This won't help your dilemma with the hot water tank, but... here's an idea for a good starting point for home made "grader blade" for your garden tractor. Our local county maintenance shop usually has a stockpile of used (replaced) wear edges for their road graders. They are approximately six feet long, and approximately six inches wide, although one end is usually 4 or 5 inches. (They were replaced because of this wear.
When i wore out the leading edge of my tractor's front end loader bucket, I welded one of these "replaced" blades in place. When I wore out the outer ends of my three point mounted grader blade, I welded one of these scrap blades right in front of (and one inch lower than) the worn out blade surface.
If your county shop will let you have one of these replaced wear surface pieces for cheap, you can weld a towing bracket (three point?) directly onto it.
If you don't want/need a roller, I can't think of a good use for the water tank, other than a water tank. (Do you have a shop pressure washer? It could now be a hot water pressure washer.)
Jim
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I got a free water heater a bunch of years ago, good tank, burned out heating elements. I left the elements in and plumbed it into my air compressor. 80 more gallons of air to supplement the 60 gallons the compressor came with. Compressor runs longer now but not as often.

Do you already have a still? 666