Should be a nice machine!
There's absolutely nothing wrong with using extension cord wire for the servo motors, pumps, etc. I did the same thing on my knee mill, and it has worked perfectly for many years. You can buy extension cords for far less money per foot (typically half or less) than plain wire from retail sources. Shielded cables are preferred for switches and encoders, but for the motors, pumps, and other devices, extension cord wire works as good as anything.
The wire nuts and electrical tape leave a lot to be desired....
Regards,
Ray L.