Kegging an ESB today, in fermenters, cider, barley wine, and a Coopers can recipe "Dark Monk" (by popular demand from a couple of dark beer mates)
A couple of thoughts for you,
Can you temp control a 50L keg?
Like you, gone are the days when I could stack 50L kegs on top of each other, would suggest you fill one with water, and move it around your brewery space as if you were using it as a fermenter.
The tapping head I linked to does indeed have a floating dip tube, so you can rack of clear beer once it has all settled, however dumping yeast/trub from a conical (or racking off in this scenario) is best done after high krausen but whilst the fermentation is still active, if you have any hops in the brew and you try this approach you WILL get blocked poppets.
Brew 45L and fill two cornies for ease of moving around or fill your other 50L (can your serving fridge hold a 50L? and if so can you get a cornie in there as well?)
Finally, do you really want 50L of the same beer? I only brew 50L when we have all the kids around for a few days (think xmas holidays)
I do drink too much, but 50L of the same stuff gets very boring, and would last way too long under normal circumstances, sure you could split the brew and play around with additions but you're not going to get a pale ale, and a stout from the same base.
These are just my thoughts applicable to my situation, you may have a very different scenario. Oh, and just give that ball a good whack with a hammer before unscrewing the collar, better safe than sorry, be careful not to damage the face of the keg where the tri clamp seal will sit.
fwiw: I'm with Meddo on ball locks, although my preference would be for A type connectors, you don't have a hole getting full of dust/crud/mouse droppings/cats piss like you do with S/D type, but as mentioned 50L is not practical for me, but if someone came up with a 20L cornie that had an A type connector I'd swap over in a heartbeat.