
I mean, how difficult can it be? The restoration staff stance (the one on the right) is the clear choice here. It looks so much cooler than any of the other stances.
There have been heaps of QoL improvements over the years, like being able to represent your guild without equipping a guild tabard, the mount speed skill becoming passive, and so on. I would love the option to apply the restoration staff's default stance to all the other staves as well, or simply let us choose which staff stance we want to use.
Unfortunately, using a restoration staff for solo play just isn't very good anymore. You can get better healing skills elsewhere, and the sustain from heavy attacks isn't really needed. If you actually min-max in PvE or PvP, you likely don't use one at all unless you're a dedicated healer, in which case I envy you for being able to natively use this cool stance.
Personally, I enjoy some light solo PvP and overland questing, and I'm forcing myself to use a restoration staff simply because I love the idle stance. Being able to choose which stance to use regardless of the staff equipped would dramatically increase my enjoyment, and probably that of many roleplayers as well, who currently have to use a restoration staff purely for its stance.
The best part is that it would be completely optional, letting everyone pick whichever stance they prefer. I can't imagine it would be particularly difficult to implement, either.