What small workflow improvements would you like to see in the future?

[handrawn]

Clever. +1.

Acorn

yes, animators would call it a light box [sometimes it might be referred to as onion skin, but an onion skin is actually frame to frame not down the drawing stack]

been asked for before

... also the liquid color FX - would be very useful from an animating point of view if that could do this as well.... in fact most of the FX previews are unhelpful in this respect...