I've had different ideas in my mind of what to do but I wanted to put it to everyone else to see if anyone has done it or if there was any different ideas.
I will put up a build thread of me making these probably.
In the end this is what I want and plan to do.
I want them on legs, I would like the top open enough to get my arms in to clean and work on, eventually with glycol jackted lines around them.
To accomplish I will make leg frame that they sit on but can be removed easily.
Turn upside down and put dump valve to pull yeast off with and a side valve to pull clean beer off.
Cut the bottom of the keg open(which when it's turned over will be the top) and find stainless lid and a gasket for that
And then wrap tightly with copper lines going to pump and tank in freezer with glycol.
Any suggestions, comments, websites that could help me with this?
Not sure I can be much help other than giving you my thoughts that led to me stick with unmodified kegs. I can tell you that you won't be able to harvest yeast just by flipping the keg upside down and putting a valve on it. The only yeast that you'll be able to dump there is whatever settles in the neck, which is a tiny fraction of the yeast cake. You need something closer to a 60° cone to harvest yeast. For me, putting legs on would only cause complications without any benefit. Making the fermenter taller would just make fitting multiple fermenters in my ferm chamber more difficult. Drilling a hole and adding a valve wouldn't allow me to use them for pressurized fermentation, and creates another area that needs detail cleaning so that nasties don't hide in the small crevices. I transfer using pressure and the keg spear, which is super easy and works great. If I want to wash the yeast and store it, I simply add some sterile water to the yeast cake after transferring the beer, shake it to stir it into a slurry, and then transfer the slurry out using pressure. It would be nice to be able to reach inside the kegs, but that would once again prevent pressurized fermentation, or use for serving, and they're plenty easy to clean even without being able to put a hand inside.
The unmodified kegs work great with the system I use, and are very easy to ferment in, transfer beer out of, harvest yeast from, and clean. Leaving them unmodified also saved me a lot of time and money, and allows me to use the kegs for serving occasionally. That's not to say that it's the right way to do things, or that it's best for everyone though.
You mentioned many things you want to do to the kegs, but you still haven't said in what ways you think these changes will be an improvement over using the unmodified kegs.
Those brew magic fermenters are beautiful to me, but I don't have $600 to spend on one when I think I can build my own for a 1/3 of that.
I wouldn't use them even if they cost less than an unmodified keg. They'd take more time and effort to clean, I'm not sure I'd be able to safely ferment under pressure in them, and they wouldn't be any easier to fill, ferment in, or transfer beer out of. The only advantage for me would be the ability to reach inside, which for me is a very small advantage, and doesn't come close to outweighing the disadvantages.