I want to suggest to add the possibility to add alpha masks for Mesh like the Alpha layer functions on BOM Mesh.
I am mostly working with Blinn-Phong, like many other creators i do still prefer that system, since PBR is simply not where it should be to be integrated in SL.
When one creates a Mesh and then goes into edit of textures we have 3 slots :
Diffuse
Normal
Specular
I would like to see a 4th Slot for an alpha mask slot.
This Mask would then allow to control opacity - Black for not visible at all to White 100% visible. It would react with grey scale. Programs like Substance Painter do it and make creation super convinient and time-saving instead of consuming.
This would allow also for an easy integration in already existing HUD systems. Scripters would just have to add the new slot as button options.
Cutting faces on Mesh and adding materials ( face slots) is a tiresome process. It also takes more render capacity on PC. With this Method in the most optimistic situation one would have one mesh and could affect the opacity in different areas with simply changing the alpha Mask texture.