"More people than not will not have computers that are not built for GPU demanding games" - well, these aren't really potential players, anybody who plays any games will have at least a, say, 5 to 7 years old graphics card, which should have not too many problems running basic surface shaders, at least when these shaders are optimized.
Also, it's true, shaderless pipelines are practically dead. Newer graphics APIs like OpenGL 3+ don't even support fixed function pipelines anymore.

If you run into problems like these - no shaders that fulfill your needs - there's always the option to write your own or modify existing ones. I'm pretty sure the specBump shader could easily modified to be adjustable.