Inkscape doesn't need this as much as some other graphics programs probably do (I'm mostly trying to push it for Krita), but since Inkscape is going to add technical drawing capabilities, it's as good a time to start considering this as ever:
Workspaces would basically be a divide and conquer approach against excessive UI bloat. Basically, 1 workspace = one saved set of settings (including toolbox items and tool option settings).
UI: in the top menu, you add a Workspace drop-down with the following possible entries: - General - Icons/logos - Art - Charts - Technical - Kids - anything else you can think of (comics, maps, whatever)
Click on any entry to switch from one to another.
Art for example will emphasize the Calligraphy tool (with eventually several settings possible and separate entries toolbox entries for the tweak tools, so you don't have to dig them up all the time). I'd also like to see a separate workspace for Composition when composition tools are created (the workspace would basically give you composition tools and a few basic drawing tools).
In workspaces such as Charts, tool option settings will automatically switch to properties such as "disable scale stroke width." You could also implement hybrids of the shape and text tools so that when you click on the centre of a shape (say... rectangle), you can start typing and editing text directly, and the text will automatically align itself with the centre of the shape, and/or the shape automatically expands when necessary (options available). Normally, such a feature would add bloat to the UI, but within a specific workspace it'd Really save time since the user would no longer be forced to align all the time. Really, this could cut down chart drawing time by half.
Technical drawing will emphasize technical tools while pushing back all the non-technical items. It may also have default grids and snap settings.
Within each workspace, you can still add another of the existing tools. This could be done either via a "configure toolbox" button or within a "Configure workspace" entry in the workspace drop-down. There, you just tick the tools you want in your toolbox.
Workspaces could also make one's life simpler when the following start to get implemented: - animation (I Really doubt most people want the animation features taking up screen real-estate most of the time) - collaborative online work environments and such?
The difficulty, of course, lies in whether Inkscape has the architectural options necessary to save and switch settings in such a way. If possible though, it will decrease UI bloat while allowing easier access to certain tools depending on the task (like the sub-modes of the Tweak tool), and could eventually allow some workspaces to have features that would otherwise be bloat in others (timeline bar for animation, maybe mini-icon galleries for if those are needed, and the shape/text hybrids I've mentioned for a chart workspace).