I have also played with the idea of an upgrade for my bucket. For me the 'rotating' valve is a weak point. Mine either doesn't rotate well or leaks. I have yet to see an economical yet functional solution for this, and until I do, my upgrade path will be to get a different fermenter. That being said, the brew bucket has allowed me to do closed transfers, and has vastly simplified my fermentation process. It is so much better than the glass carboy i was using.
Definitely the rotating racking arm is the weak spot. If the lower port were replaced with a TC fitting it would add a boat load of flexibility to the Brew Bucket, but for the 7 gallon version there's not enough space to accommodate one plus all the fittings you'd want to add on. I haven't brewed beer in mine for at least a year (when I bought a Chronical) but I use it almost continuously during 'wine making' season. It certainly is a vast improvement over plastic fermenters and glass carboys. Well worth the $$$.
When I was fermenting beer in it I did buy 2 domed lids, one with a 1.5" TC and one with a 3" TC. The Brew Bucket is only recommended to 2 psi differential but the weak point there seems to be the lid. If you do pressure transfers you'll see the lid flexing quite a bit. With only four spring clip latches, if the lid were to flex too much you'd deform it past the release point of one or more of the latches and the lid would blow. I believe (though no one at SS Brewtech will confirm) that the original spec. for the Brew Bucket was 3~5 psi maximum differential but it was lowered after a few latch failures to 2~2.5 psi recommended maximum. The domed lids will not deform like the flat lids but the four spring release latches are still a weak point. Get the 17mm drill bit and install one of their button PRVs designed to release at around 2.5 psi. I think the Brew Bucket is a great design, but it's not designed to hold any significant pressure over 2.5 psi.
After I got my Chronical the domed lids were interchangeable with the Brew Bucket. The Chronical is also only rated to 2.5 psi differential, but with 6 spring latches and a domed lid it will comfortably withstand the occasional pressure bump when you open the valve on your CO2 bottle for a pressurized transfer. I had to exercise much greater caution when I pressure transferred from the Brew Bucket with a flat lid. BTW, 2 psi is more than enough head pressure to do a transfer. I love the Chronical. I retrofitted it for heating and cooling and as I mentioned, share common parts with the Brew Bucket.
But then I decided that I really wanted to spund in the fermenter rather than transferring to a keg to spund, so I got a Unitank that gives me even more control over pressure and temperature without ever having to do a transfer until I'm ready to package into a keg or bottles. Plus all the TC fittings and parts are completely compatible between the Chronical and Unitank. Do I regret either purchasing the Brew Bucket or the Chronical? Not at all. I still use both of them, even though the Unitank is my "go to" and the Chronical is the spare for beer brewing, and the Brew Bucket is almost entirely used for wine only. They're three different tools with three separate (but overlapping) functions. Wouldn't want to part with any of them.
So to answer your original question, I'd say definitely go with the domed lid (probably the 1.5" TC unless you have a specific need for a 3" TC), don't worry about drilling and retrofitting a TC ferrule for the lid, get the pressure transfer lid kit (1.5" TC fitting with integral 2.5 psi PRV), and find the thicker O rings that
@Spartan1979 suggested. You've already started moving in the right direction switching from plastic and glass to stainless steel. Wish I'd started years earlier.
Brooo Brother
