> I want to be able to switch modulation sources with CV

Are you looking to switch between inputs A, B, C, D, or do you want a
smooth fade between the sources For wave sequencing or even modulation
routings, seems a programmable fade between sources would be better,
unless you specifically want a switch - so you're looking for an
interpolating scanner.

I'm not sure there's an equivalent in the Doepfer range, but it could be
patched with a combination of modules.

Vector mixing with something like the Intellijel Planar does this with
either audio or CV sources.

The Toppobrillo Mixiplexer (don't think it's out just yet) looks like
the cat's pajamas for this too.