I think it's an interesting idea, but it does fly in the face of what Carrara has been (and what RayDream was before).  That said, I don't think I'd be happy if Carrara went down this path, but I do note the merit of the concept.

One of the things I love about Carrara is that it is so rich.  Honestly, there are features that I use all the time now that I would never have known I needed until they were right in front of me.  I started out using RayDream 3D (it was the same idea as Carrara Basics is now).  It didn't have the vertex modeler, and I learned to build models with the tool I had.  When I jumped to RayDream Studio and then over to Carrara, I didn't even touch the vertex modeler, literally for years.  Now that I've begun working with the vertex modeler, I find I can't do anything without it.  (Of course I can, but I find that it's so much more efficient to use the vertex modeler.)  If Carrara were sold in the modular approach, I might never have popped the extra bucks for the vertex modeler, and I'd never have reached a level of proficiency that I need for both my hobby and professional endeavours.

There are still features of C5Pro that I haven't touched, but knowing that they're there, I can struggle to learn them when I need them.

I think it would be a disservice to folks who are starting out with 3D to go the modular approach, and also for those of us who are doing 3D work professionally, but not as the center of our professinoal world. 

I really like how Carrara pulls everything together and does it really well.

My two cents worth....

• Dex