I know what you are saying, but I have a different view.
I have two DAWS, an iMac and a Mackbook. The iMac was bought as a DAW. The Macbook is a general purpose PC that I use as a simple DAW amongst other things.
The iMac I have never hit a limit. Maybe I will with 8 USB channels.
The Macbook I hit limits all the time but it will mix 8-10 tracks or record at least 4 simultaneously. Fundamentally the issue with the Macbook is memory, so I get more out of it if I shut everything else down before I run GB.
The point being that I understand your point about two disks, but I am not hitting that limit at all so I am not worried about it.
Related question....have you ever thought about building a DAW on a really small Linux distro...something like Damn Small for example, or Puppy. Could it be done or would you have to bring in so many other things that it would just become bloat city?
Something like Damn Small + Jokosher on a netbook could be really useful. If I ever find myself with time on my hands I may try and build it. Or I just put the idea on forums like this and see if anyone comes back and says "I had a rainy afternoon and was bored...here's an ISO"