Third channel for i.e. alpha maps

[Burkhard]

Maybe I'm wrong, but the first time I tried out the Material settings seriously.

When using a basic Texture ( or Material ) with a bump map or normal map I'm not able to apply another third Texture like a dirt map ( i.e. an alpha image ) or a Texture overlay with a Logo / type style writing.

For the Logo I know the Label channel, but it could be usefull to set i.e. tranparency for the map like the basic material; for banners, flags...( Transparent or Specular Transmission request for Labels)

But also the same for alpha maps (png) with dirt structures, scratches and other surfaces.
So I'm thinking about a third channel beneath Textures and Bump Maps.

Am I missing a way to do this or is it a general request for the wishlist?

Burkhard