If I was you I'd build a mini WSM but use a barrel instead of the aluminum pot so it's taller and can fit more racks. I forget the barrel size that works for the mini WSM design but I think it's 16 gallons. They are pretty easy to find, and a whole lot of guys can help ya on cooks with the mini since so many have them.
I say this because you said your willing to mod the Brinkmann and that means you are handy enough to build stuff, so that's the route I'd take. The Smokey Joe is a solid platform to start off of and isn't as big as a UDS. But if you plan on doing larger cuts or amounts maybe the UDS is the better option. A TON TON TON of people could help you with learning to cook on a UDS no doubt, more than the mini WSM probably.
I'm just not a Brinkmann fan though since my first smoker was a Brinkmann electric. Only dry tough meats ever came off if it. I might as well have just slid the meat in the oven and threw a few sticks of wood on the floor of the oven. Same principle. I guess that's not what we're talking about here, but still I don't like Brinkmann products.
Weber Spirit E-310, Weber Performer, Weber Smokey Joe, Mini-WSM, ECB Electric.