There are two ways how this can be done:
1) Implement more shader nodes
for the material editor (like the "ISL shader"), like "ISL FMB", "ISL Perlin", "ISL Checkerboard", "ISL Gradient", "ISL Scratches", etc. AND an "ISL Blend Shader" to make it possible to combine shaders with a few mix modes (additive, multibly, subtract and such, maybe a blend map).
The advantage of this solution is, that it is easy to implement and also combinable with baked C4D shaders, as long as the root shader is an ISL shader (you could throw a C4D noise shader in as blendmap for the "ISL blend shader", for example)
2) XPresso
seems to be just perfect for implementing ISL in C4D because ISL is a functional language and each XPresso node basically represents a function. With XPresso i could bring the whole awesomeness of ISL to C4D, i just have to implement a XPresso node for each ISL function - which is a lot of work.
Advantages are obvious, i think - the disadvantages are that XPresso is not actually an open book for artists and not very visual (yes, its visual, but there are no little shader previews
)
)
