Oh, of course, I totally understand that
its much more fun and rewarding when you make the whole thing yourself.
The only problem I can see is that you will have serious problems making decent microchannels, in copper, with a drill-press and an X-Y table. Its hard enough in aluminium, as you're finding out, copper is several times tougher to work with.
The modded WW is something I'd definatly consider doing myself, when they finally get the Dtek block over in the UK.
Until then, got my happy little circular block running very nice
Good luck to you.