Good afternoon again!  I will not tire of declaring love to your application!  But there are a couple of ideas. 
I will arrange them in order of importance for me.

1) Saving brushes in abr format, for further transfer to Photoshop.  Faced such a problem that I really miss this moment. 
2) ”Puppet wrap” is also very necessary.  I don’t know how much it is possible to implement.  A very useful tool.
3) In the "adjustment" menu, you can add "color replacement".
4) In the "selection" menu, add the function "color range". 
5) There are sometimes not enough “actions”.  I don’t know how much this can really be done. 
6) You can also add a pen. 
P.S Thank you for your attention!

I also thought that it would be nice to have more buttons in the quick menu. But then I got over the keyboard and realized that l almost never use the quick menu.

Median filter - we will try to add it soon.
Oil Paint is complicated, maybe later...

Better Brush Editor (and other editors) - it is planned, we will maybe do it this year.

Thank you for your attention

My other work : https://www.artstation.com/artimyth
Or INSTAGRAM and Twitch  :Artimyth
And VK : https://vk.com/legend_of_falling_stars