Avatar Body Part Replacement

I feel it would be most productive to allow prim parts to replace avatar parts completely. Arms, legs, heads, even torsos, with prims in their place. This would eliminate the need for the invisible prim exploit to be needed. Maybe there be new attachment points (Such as 'ankle' for foot to completely replace a foot, 'Calf' to replace lower leg, 'Thigh' to replace middle leg, and so on) so that people wearing body parts over body parts could replace them completely with new parts and completely customize their own look.

The problem is that you can't delete part of a mesh form like that.

Add an extra tint layer to the body, and make the parts you don't want to see transparent.

You can't overload the transparency of the tattoo layer for this, it would have to be a new layer.

I don't see why you couldn't replace parts of the mesh. Lindens could make the Avatar system skeleton-based, where you have an underlying skeleton (and attachment points) And make the basic avatar the de facto default absolute minimum...but if you chose to replace a component with a prim, you could do so, and it would replace it based on that point insetad of having to use an invisprim to cover the existing avatar. It appears that anything with a transparency setting of 1 can be hidden with an invisiprim, but the trade-off is that standing over or near certain kinds of textures hides those as well, or makes your invisiprim skeleton glaringly visible and shoddy-looking.

Along with people behind you.
If it was skeletal based with the mesh somehow being made of several mesh-prims that can be replaced, it might work.
Take a large overhaul of the avatar system.