Hi Tommy,
Assuming your shop has sufficient MIPS, Real Memory, and DASD Available for IDMS to use; I'm not aware of any limitations of having one CV do all. This is also assuming most of your applications are running above the line.
And yes, you are correct saying today a IDMS DBA can carve out YUGE amounts of storage for pro and sto pools, not to mention just having to maintain one global DMCL with buffers also that don't get allocated if not used. Also, when running out of locks, more are allocated until the storage available is exhausted.
With DASD Performance today, I wouldn't be concerned about I/O bottlenecks/limitations writing journal and general DB I/O.
In my years of supporting IDMS, especially since Release 12 stabilized, I only see more than one Production CV to isolate applications (such as CAS) that have unique operational requirements.
I doubt that I mentioned anything that you weren't already thinking and others might chime in with their 2-3 cents as well
Happy Holidays,
Joe Perkins