Few comments:
- I do not understand why you are using AL profiles and AL plates, check stiffness...
- design of lower (x) rails is .... You need to grind both surfaces to get perfect parallelism, otherwise will linear bearings feel the load caused by angular displacement of both rails , put them on the top of the table, in same plane - much easier for DIY,
- design of gantry (y) - it must be closed beam - it has no sense to do a "nice look" without functionality,
- side brackets, what is the method for setting the "true" right angles? Do you expect that everything will be machined within few microns? , y length tolerance stack is problematic anyway
- foots: do you expect that desktop is planar?, machine must be stable, it looks nice, but

Before design set the requirements i.e.
- max work space
- max space for machine
- max tooling dia
- material of machining
- define what you wish to do ( mirror surfaces, engraving...)

and the start with design.

regards