I should be able to do everything I want to interact with the program without clicks or tapping with my digital tablet. To this end, I should be able to assign a keyboard shortcut for every interaction, either a toggle, separate on-off keys, or up/down by percentages or values. This would allow me to assign functions to my tablet buttons or touch ring for all interactions I desire with Painter. As it is, I'm unable to adjust opacity from my devices since you currently only support the keys 0-9 for opacity. Many other functions could be more readily enabled with this functionality.
Krita does this wonderfully. Please check their implementation and follow suit.