I think I can see where you're going with this, and I have to agree with Jim, two voices max in 104hp. But if this is a first case, I think sticking to 104hp is good. It's a good discipline to stay small at least when starting. Otherwise you tend to try and "fill the gaps" and not spend time with what you have.
All that being said, I have had a lot of these modules in my case, or have them now, so I can give you some concrete feedback. I can see totally see the idea of a bass voice in the BIA and the other voice with Dixie/Fold/Belgrad. Those are great choices, although I chose Bifold. Smaller, two distinct flavors of folder.
As your only sequencer, I wouldn't go with MD. I find it really fiddly to do anything with precision. I always recommend a Beatstep pro. Super powerful, easy to use, 0HP.
Eurorack is all about modulation, and you want to be able to have good control over that. Ochd isn't really that. My current favorite, and "desert island" modulation source would be Quadrax. Easy to mess with, envelopes, LFOs and some random.
I love me some effects in the rack, and the Versios are all great, so that makes sense too. I'm not sure I'd go with those 1U VCAs as the only VCAs. There are good single or double VCAs, with attenuator, in 4-6HP packages, I'd pick one of those.
And then some blank panels to fill the gaps. Beyond that I have opinions as to what I would put in those blank spots, but it's not my rack it's yours, so mess around with the above and fill the rest in once you determine you need something.