Very interested in this. I'm a long time Max user, but am thinking about getting into modular. This idea of a combined system (thereby not giving up the Max stuff I love) is very appealing.
I'm thinking of a system where sound generation and final mix/effects are done in Max, but having an intermediary phase at the modular. I really like the idea of developing a system where inputs to, and outputs from the modular are always the same (eg always using 1-4 out for audio, always using 4-6 out for CV etc). So then you could have a bank of generator/mix combinations in Max, and if you patched the modular up in a new and interesting way, it would be possible to recall older Max patches and the ins/outs to still work a as expected.
Coming from the Max, side it would be good to get some opinions of modules for this from people here. I think I might have some useful Max stuff around to share too.