Had to take a leave of ADSR absence to get this out but pondering your points now and might start coding this weekend 
Edit:
- Agree on mono prototype, let’s iron things out in the simpler case, make sure it’s interesting enough to proceed (pretty sure it will be!), and then add those options…
- Interesting poly patching case, definitely
- Inverted output sounds good. I think some downstream stuff might act surprising if envelopes go below 0V, so I wonder if an output rectification option might be a good idea too, as that would play well with modulators as the envelope reaches its lowest level (and the UI and block diagram has rectifiers in it for inputs anyway, so we’re not adding a new concept).