Sorry for the response "delay" but it took me time to look into all these suggestions.
To sum up, i'm now considering a 6U 104HP case that I will fill slowly depending on my needs and starting small.

@toddee
- I haven't played yet with AM synthesis, that's clearly something i'll try! I'm watching a few videos on the Veils and it looks amazing
- This "subharmonicon" concept is definitely something I'm going to look into aswell. getting a Maths was somehow a plan for the future but i'm not yet sure how to use it. thanks for mentioning it and making clearer the lesser need of the A-171-2 if I was switching to a Maths.
- Probably going to start with one voice playing around with tiny patches between 3/4 modules.
- Concerning the DT, I'm not a big fan of live sampling for many reasons (quality, portability..) but thanks for reminding that to me

Oh by the way, what is the A-183-3 for ?
-- toodee
Well, I naively though i could use it to mix multiple voices into one and send it to the output, I now start to think that might be wrong. Is it?

@Ronin1973

The Disting will give you a lot of different features to play with. You can then figure out if you'd like dedicated versions of those programs.
-- Ronin1973
Thank you for your feedback about the Disting, that is precisely what I was expecting from it

To be honest, I wasn't expecting so much warmth and detailed answers, I feel like i'm going to spend a few hours in this forum during the next months. I'm not going to use more of your time but will for sure keep you updated of the updates of this case through next posts.

Again, thank you very much to all of you for your help