Two options spring to mind, sure there are many more:
could have a toggle in the brush options that keeps the brush size constant relative to the stage
(this one could be really cool, I think) have a tool like the recolor tool but for line weights and/or even brush types - in illustrator, for example, you can pick a load of lines and set them all to be 4 pixels wide and using a specific brush. This would be super cool :-) Illustrator even has a kind of 'eye dropper' for line weight/style, so you could pick a line weight from another line, but hey...one thing at a time :-)
Because the brush size changes relative to the stage when you zoom in and out (unlike, say, photoshop), it's impossible to maintain consistent line weights so you can go full Mike Mignola https://geekandsundry.com/wp-content/uploads/2017/10/Mignola-Cover.png with your art :-)
Two options spring to mind, sure there are many more: