Actually, it could control them just fine...IF there was a quantizer. Otherwise, getting discrete scalar steps is a total pain. There's a much bigger issue with that sequencer, though: it's an Analogue Systems device. AS (not to be confused with Analogue SOLUTIONS) decided early on in the creation of the Eurorack format to adopt a weird rack spacing that results in their modules being 1 1/2 hp off of everything else that exists in Eurorack. Now, if one uses sliding nuts to rack up modules, this isn't a problem, except maybe at the row ends. But if you have tapped rails...ohmygawd...
Anyway, size-wise, I would say the rack is just fine. However, the critique about what's in it by the above poster stands. There's lots missing: VCAs, multiples, mixers, i/o, pretty much anything utility-wise that makes a modular function. Oh, and that Pittsburgh phase shifter is also discontinued, along with the other non-gettables.
My suggestion: start over, same size. Don't concentrate on the 'sexy' modules; instead, pay more attention to the boring bits, then fill in with the sexy stuff once you've got a good supporting architecture. And keep your module sizes down as much as possible, because 3 x 120 isn't as big as you might think. Also, the above poster's note that you might be trying to cram too many different functionalities into this build is pretty spot-on. Not saying it's not doable, mind you, but it'll take a considerable amount of care to get a full-on all-in-1 box into that sort of space. It's also distracting to try and build something like that without a great deal of experience...you may be better figuring out just a handful of things you want this to do, and sticking with those. Also, a good way to proceed is to partition out the empty rack, allocating specific areas for major functions and then trying to stick to that partition plan as best as possible. This way, you're thinking about the actual function blocks in terms of available space, and then you'll be more likely to go with smaller modules...and therefore, more potential in a smaller space.