I’ve seen them in the place of the tab key but never on the home row.

Personally, as a long time Vi user, I think you’re better off mapping the caps key to Ctrl and using C-[ for escape. That leaves you with many more Vim insert mode commands within easy reach.

E.g. C-r <buffer> — to put a buffer

C-h — backspace

C-i — tab

C-m — CR

C-xC-f — complete filename

Etc, etc.

h,j,k & l are really only the simplest od vi navigation keys. Once you know how to, say, jump to 3rd paragraph or to jump or to the middle of the screen you won’t use them anywhere near as much.

Much as I love vi navigation owning a Pok3r keyboard has shown me how annoying it is to not have dedicated cursor keys for GUI applications.