Another concept is the wooden box idea such as the makerbot or mantis. It could be bulky but it might also add a lot of structure and rigidity and still be affordable.
It might be difficult to work inside a box with a CNC as well.
One way of the other, I came across this version of the mantis.
It uses a box for it’s entire structure.
This could be very favorable for portability.
Also, if it were fitted with a door in the front, this could be a cool solution for dust and noise control.
I think if this were fitted with some sort of vacuum, it would be a great small machine.
The box could be MDF and the door acrylic.
Even if most of the box was removable for when you want the machine to be more open.
Portable, quiet, clean and affordable.