Dynamic buttons - simplified toggle state

The general reason for not supporting settable "on/off" states is that such states are typically reflections of what goes on in other software (for example Pro Tools), hence, it's very easy to code something where the state ends up not being in sync with the external state. For example, you code a button that toggles its own state between on/off and controls a track's mute state. That works fine so long as you only use that button to toggle the state. But the moment you change that external state (the track's mute status) externally, for example by clicking the mute button in Pro Tools, the external state would have changed, but your internal state wouldn't have.
For this reason, as part of the Developer Program, we teach how to build apps that rely on external state by never duplicating that state, so that you're sure what you're looking at is always true.
What this brings is higher quality commands to the entire community and ecosystem. Building "semi-dynamic" commands that are allowed to toggle their own internal state but can't rely on external state in a reliable way would be something possible to build, but we would have to make sure that we build it in a way that doesn't adversely affect the community by swamping the free store with non-reliable components.

Just to give a little bit of insight into our thinking here.

What would be the kinds of things you'd like to control? The more specific, the better we can try to invent ways to achieve it for users without sacrificing quality.

What's the use case you have, Brendan? The general use case is hard to support for the reasons mentioned above, so it's helpful to know more about what you'd like to achieve more specifically.