I think the ability to swap the location of the brush sliders and toolbar would be a great addition. Personally, I would much rather select tools quickly using my thumb on the left side of the screen, while using the brush sliders with my pencil. I tend to already use the pencil on the brush sliders for better precision than dragging a finger provides, and having the tools on the left side would make them much more smoothly accessible as I draw (for swapping quickly between brush and eraser, for example).
I know this is similar to the old UI layout, but that's a good thing IMO because when the UI changes were implemented, I saw a lot of users were missing the old layout, so making something similar an option once again would be great for them as well. I'd like to note however, that I'd definitely prefer the brush sliders to be on the top of the screen where the current toolbar is; the old version with the sliders on the bottom was always uncomfortable to me and I'd tend to accidentally move the sliders. However, having the option to put it on the top or bottom would be another welcome addition for many, I'm sure!