I've been reading with interest about this exciting project. As a programmer that grew up during the golden era of hacking, I love the fact your trying to rekindle that spirt of development and hacking. While this may be something you're addressing once you've got more hardware, I'm concerned that you're too focused on hardware and not on software. Something I've noticed is most people longing for the golden era are hardware guys, and they naturally focus on the bits that got their juices flowing. I always found the software end more interesting, and that is (from what I can tell) the area you want to encourage.
I hope that you will be producing a very easy to use tool chain as part of this development. This should not be just a command prompt and vi. We've had those available for years - and fin. Has the Pi got its own IDE and debugger? This part in my formative years was more important that any hardware (and really still is!). The iPhone platform with Xcode has reminded me how much this matters. I have had a PC on my desk with 10-100 times the performance for years, but the first time I got something up on that little screen the desire to create was rekindled. Though the tool chain is basically the same as Linux has had for years, they bound it all up in a quick and easy to use manner - online/local help a keypress away, intelli-type code completion, 10 secs to compile->debug->run. Debuggers that actually stop the code you've written and allow easy inspection of what is going on. These make more difference that any hardware.
You have a golden opportunity to solve this problem, as you have a controlled platform with known parameters. Please don't create another wonderful, but unusable device!