Thanks very much for your advices Lugia. Your remarks gave me a better understanding of the way a modular can be built up.

So, considering your suggestions, I modified the rack.
Here is the v2 :
ModularGrid Rack

And then, a likely sufficient but cheaper version (2000€ being a maximum amount, at least as a first step... :))
ModularGrid Rack

Your final judgment would be very valuable.

'On ne devrait jamais quitter Montauban' (Fernand Naudin).
https://soundcloud.com/petrus-major/tracks