At sufficient head pressure that would work. Main design issue is that it isn't optimised for most of the heat load being in the centre of the processor. The pressure required to maintain a sufficient flow rate through this would be mad.
As a quick fix, wrt
this image, mill a slot bottom to middle left and another top to middle right. This will leave many, many parallel slots and considerably lower resistance.
Regarding manufacture. First you have to persuade a machinist he wants to do this. If he's you or a good friend this will be viable. If going to a professional company, expect to pay over £500 for this. A single piece cut on cnc is rarely financially viable as the man hours involved are considerable. If you wanted 50 of the things, you'd be looking at 5k or so, cost per unit comes down sharply with cnc as most of the time is spend on set up. So unless you have access to a lab, give up on cnc and accept you'll have to cut this by hand.
On which note. That looks like you're milling channels 1.5mm wide by 4mm deep. That wouldn't work in brass, it definitely wouldn't in copper. With small milling bits, below 4mm or so, the best depth you can hope to cut is about half the diameter of the bit. Obviously this has a negative impact on surface area. The xspc edge was an attempt at doing something like this, they broke so many milling bits that they had to cease production. The block was damned good though. Oh, when the milling bit breaks, it tends to write off the piece of copper as well.
Most blocks today have a copper base with a vaguely circular indent cut out, and then a lot of 1/2mm or shallower slits cut parallel across. That's done with something that looks a bit like a thin grinding disk mounted with the axle horizontal. It'll cut these happily, but doesn't plunge well.
The normal waterblock design calls for a piece of 2 to 5mm copper with some basic machining, and a thick piece of delrin with more intricate shaping as delrin is a hell of a lot easier to machine than copper. The more advanced ones are sandwiches of various layers.
Waterblocks are difficult. I've put a few sketches together and shown them to my local machinist, at which point I discovered milling machines don't work quite like I expected them to. Curves are difficult by hand too. Don't be dissuaded, but getting this manufactured either means you cutting it yourself or you persuading a friend to do it for beer and pizza.
edit: I haven't given up on my plan of making waterblocks, but I have revised it to start with chipset/hard drive/ram blocks first as they're much easier. Specifically they can be considerably lower performance and it doesn't matter. So make these first, then progress to more exciting projects. I think I'm going with 16mm acetal top, milled, with 3mm copper base. Joining them together is hard, solder has its own issues, I haven't worked out how to size O rings or how to cut curves on a mill, so currently planning on using epoxy. Should have these made by the summer.
