Then I'd finish what you started. Yes, they arent the greatest machines in the world, but they do work if constructed well and, if nothing else, will get you up the learnng curve. And the Mk1 machine can be used to make the parts for Mk 2. I don't know the details in the book, but don't buy the motors/electronics without discussing it frst. Why? because these things change quickly, costs are coming down and its likely whats in the book is out of date already. Plus those parts are likely to migrate to Mk 2 so its wise to plan ahead to ensure a sensible investment, or at least know what the sunk cost will be if you choose not to migrate them.

The problem with the Internet is sorting the wheat from the chaff... yes, you'll find a lot of people who'll say those machines are rubbish, don't bother... but often they'll be people who've been 'in the business' for years, run machine shops with several jobs going at once, etc.. from their perspective they are right, but that doesnt change the fact that as a beginner's machine it serves a purpose. There are also those that disdain building anything you haven't designed yourself, on the grounds that unless you have done so how do you know it'll work? Again, there is some truth to that, understanding why something is the way it is is important, however my argument is that you can spend forever debating the finer points of layout and design. Build something, use it, learn its weaknesses and use that knowledge to develop better parts or design a better machine.

Any machine will cut anything given time and a very limited depth of cut. Yes, that machine wont cut aluminium the way a bigger/stronger machine will (actually it will, but you have to do it in very small cuts so it takes a long time and accuracy isn't great, but it will manufacture the parts for a Mk2 if thats what you want to do).

So go for it!