A quick note to answer part of your question:

I would still consider putting a bare minimum fallback in the effect file. You never really know what card will be running it. For example; it may not support (3) texes per pass, alphaops, or the order of args.
I put (2) fallbacks, (1) being the colormap and 1 detailmap, (2) being just the colormap.
Even if using d3d_shaderversion, I would still add a fallback technique in case something slides through.

As far as the amount of textures, passes, what-not. I am making a point to script in the ability for an "option menu" where the number of textures blended, the detail amount of the textures, query what pixelshader is available, etc, can be user selected.
I believe it should be up to the end-user to decide how much they want to tax their system and to give options to ensure that they will in fact be able to run the proggie.

I'll try to get back to you about adding more textures.. it will probably be via Private Message, tho.

Eric