I'd rather see automation envelopes happening than yet another hacky automation command. Especially for slow and long changes, an envelope that is always visible would work much better visually than a pattern command that is only found in a single spot and then continues to do its magic in seemingly empty pattern cells.

For what it's worth, you can already automate plugin parameters through instrument envelopes - see https://forum.openmpt.org/index.php?topic=3056.msg39765#msg39765 for more details.

No, i agree! — Envelopes assigned to plugin controllers is an even better idea! The only thing that would slow down development is the fact that a GUI would have to be created as well as the actual methods.

And i didn't know about macro adjustments with envelopes! I'll hafta check that out.

As you probably know by now, I'd rather implement something that takes a longer time to develop than something that may be quick to implement but will add a lot of complexity or legacy. In this particular case, commands that are active over the during of several rows would add quite some complexity to the playback engine and would be difficult to keep track off by the user, so I'd rather spend more time on a proper solution that is also easy to understand. We cannot get rid of existing complexity but I want new features to not inherit this complexity by restricting them to the existing UI - see for example the implementation of tempo swing, which was previously suggested by users to be based on stateful pattern commands, much like your suggestion.