I like the idea but I would rather have a client that I could use on my machine then plug in the modules I needed for what I was doing.  Working through a browser seems like it would be clanky and slow considering the the processing you need to do if you were working on a 3D project.

Ok what I mean is make a client that I can use on my computer, then develop modules that I can plug in and use as I need them.  You give me the client for free and charge me for the modules that I use.  So say I want to do a electrical plan.  I subscribe to a service that has that module for your client.  I pay for however long I need that module then I cancel the subscription.  Rather than selling software you in a sense rent it out.  Web base design is nice and all but keeping it all in the family is much more preferred.