Comparing the cases below, B is more convenient, especially when working with lots of bones.
A (current behavior):
B (more effective way):
IMHO, current behavior should be kept, so maybe we can operate B, for example, by hiting Alt key? Just an idea coming from some real projects. FYI.
BTW, for some "bone-only" fields (like below), maybe it's better to support eyedropper feature on them as well?
Ehhh, really tricky! Basic issue is that bones aren't data-blocks which is the only kind of data the eyedropper can handle. @Campbell Barton (campbellbarton), I think we could make eyedropper support non-ID struct though? (Alternative would be to make Bone/EditBone IDs, but this sounds really troublesome)
There are more issues with automatically setting target and bone (sub-target), but that's for later ;)
It may be possible, we have prop_search which knows its searching PoseBones, so the UI could detect this case then show an eye-dropper.
As for picking, the operator could support a sub-target... however we would want to limit the bones selected to be the armature (which is already defined) - in that case it may be better to have a data-picker for bones (can be generalized to object-data-elements - so it could be used for other types in the future - if they're added)
It's more a feature request to me, which isn't really good place here. If someone from the developers wants to pick this up, please re-open and assign to self.