Sure you can, but it's rare to see a GUI app built keyboard first and specifically optimized for the productivity of power users. The list of apps that do this successfully is a tiny fraction of the total.

- Excel

- 3D modeling tools

- Adobe Creative apps

- Programming IDEs

- ?

Also, if you are focused on that metric: the productivity of the power user, then in many cases adopting a more modern GUI framework will not necessarily make it easier to achieve that goal (and in some cases may make it harder).