When I first got the Diezel FL cab at I didn't like it as much as my old faithful a Mesa traditional cab.
I swear my ears must have adjusted .. now it's the other way around.
The FL is something special, highly detailed mids , touch responsive, loads of deep bass - just very controlled.
Cab is great, I'm just personally not a fan of the k100's but I tried them in a mix and it was tolerable for my tastes. They just didn't have the break up v30's have and I missed that.
I say just keep the Uberkab and buy the Diezel cab.
You already know my opinion through our PM's. Get it, try the 4 K100's, when you find them too neutral and lacking cut, swap in 2 V30's like you just said.
Don't know that they bring the bass, but they sure as hell can handle it. I had a Herbert for a little while and the K100s handled every bit of the deep knob with zero flub.