Hi Cedrik,
Genode's philosophy seems to be "don't deny complexity, but organize it". So it would be an interesting challenge: would implementing workspaces entail big changes in nitpicker? in wm? How to reconcile the need for a low number of source- code lines, with the need for additional, complex features -- it might justify offering several w.m.'s (which I think is already the case), of varying degrees of complexity, so that users have a choice between high reliability (but somewhat restricted) wm's and more feature-rich wm's implementing workspaces, at the expense of possibly more bugs.
the design of the existing architecture (nitpicker + wm + layouter + decorator) already anticipates these concerns but the current version of Sculpt still hides this potential somewhat. I remained rather low-key about it because we had to nail down other (non-GUI) aspects of Sculpt first.
The current architecture already has the right hooks for implementing a rich feature set, including workspaces or a panel. It's just a matter of using (and possibly refining) those hooks. During 2020, I plan to put the GUI architecture more and more into the spotlight, possibly via a couple of Genodians articles.
The dual-head support is a different topic though. This one calls for non-trivial interface and architectural changes.
Cheers Norman