Raised plywood false floor for heavy equipment usages
My first guess was, with at least 667 pounds on a caster, there's no way 1/2" plywood is going to hold up.  I'd want this plan stamped by a PE and a certificate of insurance for their E&amp;O policy.  

There's information available for uniform loads on plywood for general construction but not for concentrated loads.  I would not put much faith in something used for dance studios holding up to industrial use with heavy machinery on casters.  

I stumbled across this thread:  

https://www.eng-tips.com/viewthread.cfm?qid=229324

There's a linked PDF in that thread with a photocopied page from a report on concentrated loading of plywood.  It shows you might be OK with 5/8" plywood supported 16" OC or 3/4" plywood supported 24" OC.  The APA (American Plywood Association) might have better info available.  Note the difference in the dry and wet values in that PDF.  Obviously you're going to have to use plywood that's strong and will stay strong exposed to a lot of moisture. 

If your layout is not going to change, you might get better support if you space the joists closer in the aisles and under the casters.    I have seen this done in very old industrial buildings built before structural steel with wood columns, beams, and floors.  

Is there a plan for ventilation / dehumidification under the floor?  I would think that's going to be very important.