Easiest solution for your plates is to get a fellow member to make them for you on their router (This is what I did). In which case it's probably cheaper to find someone to make your plates and have them sent directly to them than send them to you and then on again.

If you design your plates so they only need to be milled on one side you will make the job a lot easier.

If you do make them yourself then make them from ply/mdf/wood first before you attempt to make them from aluminium, it's a good idea to prototype in wood first anyway I didn't and in the end I had to do some post processing work because of it. My Z axis plate was catching the BK fittings limiting my travel a simple mistake due to using wrong carriage model for my Hiwin's and making last minute changes before cutting without noticing the Z.