Why can we add vertex alpha if there are no proper shaders?

I have been playing with procedural mesh-building, and have gotten to the point that I am satisfied that my normals are calculating correctly, my UV mapping is good, and I want to bring it to the next level by adding additional triangles that use the vertex alpha value to blend.

Unfortunately, the shader projects that I have found that actually use the alpha value also seem to touch the whole mesh with a fade, rather than only the triangles assigned to the low alpha. (Also some funky clipping going on that doesn’t happen with non-fade shader). <-discovered just now this has to do with the draw-order vs depth.

Does anyone have a simple solution to this? Seems odd that we have a piece of data that is not easily used.

Thanks in advance!
ps. my searches have let to lots of complicated shader programming that I am not really up to. I just want one that uses the alpha for the alpha!

Simple things sometimes means a lot of work, i would suggest splitting mesh into 2 - one with trapnsparent triangles and other with standart shader.