So not getting any response in the CNCRP Subforum,

Waterjet cutting of the parts in red in steel is out, multiple quotes of $2000+!

So, aluminum it is, because I can cut that myself on my existing router.

Would 6061 flat enough in 1/2 inch material thickness for Gantry sides, and the X-axis plate?

Or should I go with MIC6, is MIC6 strong enough for the same pieces?