Gotta agree here...this is a little too 'undercooked' at this point. 'Take it slow' is wise advice, to which I would add 'look at other examples', which is another great asset of MG, although you need to be careful to check ones done by the numerous users on here who've got some experience rather than using random examples.
As for sequencing...for something rather tight on space, you might even consider going outboard, since sequencers are usually space-hungry things. Have a look-see at the KOMA Komplex; that, in combination with a Monome setup, would be downright scary.
External processors aren't a bad idea, either (would let you lose the Magneto and free up buttloads of hp!), but remember that the right way to use them, in most cases, is to employ some sort of send/return module(s) that step down the signal to the effect, then step its output back up to re-insert it into the modular's signal level. Also, not a bad idea having that 1U tile row there, but keep in mind that Intellijel's tile format locks out all of the other tile choices, whereas you can kindasorta fudge Intellijel tiles into the 'conventional' format with a little ingenuity (and a bit of hacksawing on the mounting holes on their tiles).