Jim's spot-on here, really. 1 x 84 hp is just too tight, for one thing. Plus, a Mantis is pretty cheap...not as cheap as the 2 x 140 Ulicase, mind you, but $335 for 2 x 104, powered is a pretty stonkin' deal. And Tiptop even thought ahead for live users, as they've got their own gigbag customized for the Mantis. You also regain the 4 hp used by the uZeus, too.
Using a bigger cab can also help with sufficient space for some large modules, such as Maths. You won't have to be as concerned with what space those 20+ hp-ers are burning.
-- Lugia
Truth is I wasn't planning to go too big in general, I want to keep a small yet packed system since it's going to be further processed in a DAW.
I also am thinking that the sentence "to integrate 0-coast to the rack" was not the proper phrasing, I am not planning on physically moding 0-coast onto the rack, also why I was going for something smaller.