Fixed Gantry won't give me the versatility. I'm thinking of a spindle motor/gearbox like from a mag drill. The delimma is z axis design. Yours is the closest to what I've imagined but can it be modularized. Something I could swap out for high speed operations. I've even considered electro magnets to lock it all down during drilling. It's probably not necessary with your design although I don't think I would use any aluminum.

Thank you for your thoughts. You've built a great resource here.