Controlling more stepper drivers than I have outputs for?

A post to the Ahha group brought no replies, will try here. I am looking
into an application where I would need to control a minimum of 6 axis,
up to 8 axis, in 2 axis pairs and with no more than any 4 axis needed at
any particular time. Ahha will only control 4. I would have all motors
and drivers powered, want to be able to switch step/dir lines without
getting any jumping from switching noise. Also need to maintain current
line status, whatever they might be at the moment. Would like to do this
with off the shelf stuff, even if I have to build from the component
level. This will probably be done with Gecko drives, which offers the
choice of steppers or servos.

In a nutshell, I want to automate a lathe with multiple slides, and
control a robotic loader/unloader.
Reason for wanting to do all this in Ahha is I want ALL info related to
running a particular job in the G-code file. Yeah, going to be
interesting setting up programs...<G>
Goal is to reduce to a minimum the lot size needed to justify the
automation. Do not want to get into PLC's and having to load separate
programs.

Jon A.