Havent been posting anything for years... Good to see some old names in the forum.
I cannot insert or upload any image references here so I will just explain in words...

1, I like the square color picker in AR, it allows me to match colors with certain value (better than Photoshop). However the color slider, although it looks simple and clean, seems totally useless to me because I cannot see what color I am going to get on the slider, especially the RGB slider!

So please add color to color slider! The function should be more important to how it looks.
Please also make the color picker a bit smaller... it takes too much space.

2, Color balance filter please! This filter is very important to many digital painters.

3, As far as I remember, in AR4 we when we right click with a certain brush, we can get the preset list of the tool (like Photoshop brushes), allowing quicker brush picking. But now we will need to click on the preset pod, then click group, slide down for the brush... can be really bothered.