Laser positioning? Gantry or lenses?

A rather charming lady friend of mine has been asking about a machine to
"cut out all kinds of fabrics from computer designs", since she does
professional costuming, it's going to mean everything from silks to
latex sheet (a nasty one to cut with mechanical tools), so I was
thinking inert-gas/20W laser.

Now this is something I've been thinking of for a long time, my idea was
to build a general purpose gantry that will do everything from (wood)
routing, to plasma-cutting to using a laser. Doesn't need to be
incredibly accurate, 0.5mm is more than enough. However, this is going
to be rather complex and cumbersome to build, and in light of my friend
now pestering me much more, I'm pondering building a laser specific
machine for just her. So this begs the question, if I'm using a laser,
can I just get away with some lens arrangement instead of needing to
build a whole gantry? It is a big area 3x5foot, so I'm worried that at
obtuse angles the laser will be more of a ellipse than a dot, but is
this at all possible?

How would you achieve driving/controlling this as the angle of the
mirrors would not be a linear relation like a mill axis, so you wouldn't
be able to drive it with say, mach 3? Or is there some neat mechanical
trick to relinearize it? Or am I just being silly because the shifting
focal length of the laser will not allow it?

BTW> I won't feel like a real eccentric inventor until I have a laser! :)

Thanks!
Abby