Hey Robert,
the answer is no respectively to both of your questions 
I was asked for simple possible solution, my answer is here.
The solution in the industry would be using a stepper motor with integrated brake, that passively prevents the stepper turning as soon as power is gone. Such steppers are available as standard part, but not the Elite/Masso stepper as found on the Elite machines.
A quick workaround would be Jim’s method which is putting a block of wood where the spindle could come down. A real fix would be to use the restoring force of a constant-force spring (see balancer / positioner / retractor). There were some propositions in this forum, e.g. here, here, and here. Here is a recent solution.
I think if you want to retrofit a brake like this to an existing Elite/Masso Z stepper, then you can simply continue to follow this thread (@ChrisS attempt).
Note that in terms of safety, a spindle coming down with gravity on emergency stop or on power loss is a nightmare. Here I wrote about Emergency Stop Categories.