This can only be achieved IF the DAW in question sends that data in the first place (and then we can start wondering of how to decode it).
In case of Ableton Live that is not possible by default - it might be achieved if you have MaxForLive, and you design your own M4L device which will look up in specific stuff of Live's API - and even then Im not sure if its possible. Thinking about it, I really think even then, its not possible, the reason being I dont recall anything in Live's API referencing which parapeters are midi mapped and which are not in order to retrieve that data and send it to Lemur.
Frankly, you dont need a Lemur scripting God - you need a feature in DAWs which doesnt exist (at least in those I know of and have worked with).
For Reason I really don't have a clue although I suspect it wont be possible for the same reasons.
In situations like these, and given the "nature" and freedom that Lemur provides why dont ya just make a Lemur project that controls ALL the parameters you wish to control and show-hide elements if the surface gets "massively clogged" and full of controls?
My current Ableton Live - Lemur controller features around 10 midi channels x 127 CC numbers = 1270 parameters. No need to re-map anything on the fly, anything I want is already there and of course named after the mapped parameter.

Cumbersome? Yes it is. It has taken me months to design this "template" project in Ableton and Lemur just came to "unify" what i was already controlling with 3 different controllers, but yes its "doable".