There's only four things that should change the stroke/line width:
- Stroke width
- Line width tool
- Z depth setting of a layer/group
- Zoom Camera tool
This (the four things above) is how a cel would behave in the real world and it leaves the artist/animator not having to worry if all their line sizes are proper. Draw at whatever size you wish and scale later, transform your layer/group how ever you want and never have to worry about your line sizes unless you alter one of the four options above.
EDIT: Basically disabling the Transform Layer tool stroke altering feature by default. This basically is about the same as my other post but explained much better and why the purpose. Otherwise it creates a lot of work to resize multiple layers in a group. It also makes your work look more professional without the worries that you just altered something with the Transform Layer tool. Specially for beginners who may not think of these kind of things.
EDIT 2: Added Line width tool (forgot about that)
Multiplane Camera
