It’s ok, I should probably have given more concrete example of the case, as it unfolded; but will do now then.
Well, this would be exactly what I don’t want to happen; as this should create bad infinite loop in Blender. However, I’ve found out that ‘playing out’ with the danger, seems to be actually the current unique way to automate the creation of Mirrored Vertex Groups.
Well, this seems to be an interesting complementary idea; well thought. Like, after the automation is done and the Mirror Applied, there seem to be apparently no reason to maintain their cloned names (Bones and Vertex Groups); it sure will add extra work, but the worst part would have been done already (which is on a more automated Mirrorring process.
I have been gambling with infinite loops in Blender, for instance, playing with very low Influence (on certain Armature Rigs with Bone Constraints in conflict with Parenting); in practical terms, it seem to be pretty useful. But I’ve never done this with Weight Painting; this is the first time I purposely create a (most likely if my memory is correct) infinite loop which is being blocked just by a 0 Value on Weight Paint. As I’ve tested, it seems to be working, even without differentiation on the names; but it will most likely be wise to make the changes to prevent future, plausible issues. I’m just not very sure about those Bones (.L/.R)… if they won’t try to make new, fresh Weight Paint Vertex Groups on their own, since the originals would have “vanished” (changed names). There is a possibility that it might be better to maintain the cloned names as they are.
This is not the first time I’m presenting this WIP setup on the forum.
What is happening here is not too complicated, but it’s also not very conventional I guess:
There are Deforming Bones (for the eyelashes Mesh Object which doesn’t show up here) that are (or should be at least) following (from their Bone Heads), through Copy Location Bone Constraint, singular Vertex’s Vertex Groups on the eyelids Mesh (which is on another Mesh Object, the body). Those Bones will Deform the eyelashes, not the upper eyelid; but they will follow the lower limit of the upper eyelid. There are as many single Vertexes’ Vertex Groups on one side of the face as there are Parenting Bones there for the eyelashes; so about 15.
Note: there are some extra Object Modifiers (on the body Mesh Object) that are very required, but that do not relate to the issue on this topic. For example, Shrinkwrap Modifier to the eyelids Mesh (a whole Vertex Group of its own), followed by Solidify Modifier (same Vertex Group); there’s also need of a Modifier that ‘glues’ visually the eyelashes limit with the upper eyelid limit, that’s another Shrinkwrap Modifier, either to the eyelashes or to the body Mesh Object, but now on a new Vertex Group, respectively, either to the limit edges of the of the eyelashes or to the limit edges of the upper lid; cannot be both — this would trigger horrid, glitchy infinite loop.
This whole setup is a bit more complex and require aesthetic refinement and tests; but at least the technicality of it in Blender, now has reached complete success, as this Vertex Groups automatic Mirroring was the last issue I was having trouble with.
This setup is supposed to be used with Shape Keys for the face Mesh and/or facial expression Deforming Bones Rig. In the video below, you’ll notice that I’m not moving any Bones, but actually, the mesh itself: naturally, other Bones and/or Shape Keys will have to become responsible for this transformation later on. Sure, this is experimental; if the final aesthetical result is good, maybe it pays off all the work and research as a good method; otherwise, I’ll have to try something more conventional I guess. But I’m optimist now.
Thank you again for your feedback.
To control armature with a mesh and the mesh with that same armature… at the same time? 
