Hi Clef,
Firstly the 2.2kW spindle is way overkill for what you want and its too big for a 12" machine. An 800W unit will be compact and do the job. I use a 600W DC spindle (see images) for that sort of thing and its fine. Your design will have to have a structural bias. A) either towards aluminium which means it will need to be very very stiff B) towards timber and plastic which means it can be less stiff and simpler.

Now a 12" machine will use 4 or 3 motors. The size you have picked is very grunty and 4A. If you use 3 motors then the absolute max current is 3x4=12A but this is unlikely to occur so a 10A supply is fine. Your controller is 24V so you need a 24Vx10A supply so that's easy. Now if you use 4 motors 1) The same applies as the twin motion system you only need a smaller motor on the twin drive say a 2A motor. There is no need to have 6Nm (2x3Nm) on one axis and only 3Nm on the other.

I just noticed you say 4x motors so this comment is applicable. So pick smaller motors for the twin drive. I run this machine on a single 24V 10A supply and its quite comfortable even though it has 4x3Nm motors... On my current build I have downsized the motors as with ballscrews the forces available are very big 100's of kgf with smaller motors. Once you try to get power supplies over 10A they become very $$$. You have also picked hybrid motors and unless you are trying to make a very fast machine I don't believe the extra $$$ for these are worthwhile. The $$$ can be put into better bearings or spindle which is better spent. If you want extra speed then a 24V system is too low a voltage. Use 48V. With the $$$ saved on hybrids go higher again 60V and the motors will spin fast nicely. Can't comment on the DDCS , I use UCCNC and I'm very happy with it...hope that helps. Peter