1) The plasmashell is pretty unpredictable now. In the sense of RAM consuming from 100-120 Mb at start to 350-450 Mb a few days later. It's not good for home and work computers. Is it possible to limit caching or something like that? Settings for memory usage policy, maybe (as in Okular settings)?
2) The plasmashell is crashing due incorrect widgets, it happens. I think, it would be great to select some comprehensively tested basic widgets like a panel, system tray, main menu, pager, etc for execution into the first, main plasmashell process, and all other widgets put in the second plasmashell process. Thereby the desktop will be work even if an incorrect widget will crash second plasmashell process.
Also, tested, stable widgets can be placed on first lines of search results in Plasma dialog window.