Jim - I looked at this yesteday, but thought that I knew nothing about lasers ( the cutting/engraving type) so I would leave it alone - but nobody has answered.
Mach 3 is perfectly capable of controlling what you are doing. It can certainly move you table with the work on, in the correct manner, and there are many outputs avaiable to switch your laser on and off at the correct time.
There was a post a few weeks ago about delay on the M3 (spindle motor on command) which someone was using as a laser trigger, but that was resolved. You have a choice of already written on/off routines M3,M4,M7 and M8, which switch relays on and off, or you can write your own macro.
There are also a number of people engraving "circular" objects on rotary tables - Mach 3 can do it.
I don't really know, but I think it would be a simple job, if you can buy a commercial laser for engraving, then fit the business end to the spindle of your machine and away you go.
There are a number of programs ready written for engraving work, and I am sure there will be one for lasers.