I did an undergraduate electrical engineering degree some years ago. Building a CPU much like this one was the final project in our second digital design class. The difference here from the usual approach, as they point out, is that this is a gate-by-gate design you could assemble out of 74-series logic gates on a breadboard rather than the more common Verilog/VHDL designs that target FPGAs. Definitely a more tedious, time consuming approach, but I'm not convinced it's more conceptually difficult. By the time you're building a CPU, you've probably already built the component parts like the adders out of pure logic gates, anyway.

Not to say that this is easy, but I think you'd find that a whole lot more people are doing this kind of thing than you might think.