Main concern right now from clients is the lack of an 'Esc' key

Assigning to Omri to please look into.

Thanks!

Discussing in email

Separating out escape special case to address more urgent needs ( issue 900924 ).

ChromeOS needs a full key VK as one of the user-selectable VK options.

Cursor up, down, PgUp, PgDown, Home, End are just as important as ESC to make the slate models useful in productivity apps and Crostini. Function keys (e.g. via a FN key to save a row are important too, esp for accessibility reasons). See https://groups.google.com/a/chromium.org/forum/#!topic/chromium-os-dev/9EOVBq7efDg for further info.

Thanks for the additional feedback.  Also see related issue 853965.  

I actually would not want users to have to choose an entirely separate keyboard -- this creates a huge duplication, especially as we consider many additional languages.  Perhaps we need a kind of modular extensibility, to let you bolt on sets of keys for different purposes.

A "full" button that works similar to the other modal switches in the top line of the keyboard overlay would be fine.
This should be relatively easy as up, down, pgup, pgdn, Esc, home, end, ins, del and the function keys all have the same keycodes across all keyboard layouts (~languages).