I think Simon asked for my opinion, so I'm writing a few comments below.
Initially I thought the proposed walker change would have huge backroute potential, but it doesn't seems like that after some consideration and the discussion above. Still, it's not something that can be automatically checked.
I only see a minor increase in conceptual simplicity with the change, I think the amount of time it takes to learn the skill is not going to differ much.
As for functionality, it's hard for me to judge which is more desirable. I can see a slight advantage of the new behaviour with builders and platformers (behaviour is consistent even during and after shrugging), before it was possible to turn a builder/platformer after shrugging, but it was very precise. My hunch is that if you cancel a builder/platformer, often you don't want it to walk off the (possibly deadly) ledge in puzzle mode. In multiplayer mode I believe I do use the current behaviour however to speed up the Lix once the bridge is long enough, though jumpers work there just as well. Applied to blockers I see the above argument that especially near a ledge, you'll want the blocker to turn when releasing. For all other skills it doesn't seem to make much of a difference, except for the consistency when they are about to transform back into walker: E.g. when a basher or miner is about to finish, currently you have to wait for it to transform into walker to turn it around, while with the proposed behaviour you could just assign the walker whenever.
So overall, I'm almost indifferent to the change. It seems like it has a slight functionality advantage, but comes at the cost of checking levels.