I should add that I would likely stick with OpenStudio if I weren't doing so many / such large models.
If you already know how to code in the Ruby programming language then you should definitely use OpenStudio. Then you could build your own add-ons which could serve to implement your preferred HVAC systems essentially automating the process I described before.
Also in the works for OpenStudio is a merge / split zones function which would eliminate my need for DB. The most powerful aspect of DB is the ability to draw one large block and subdivide that block into zones by adding partitions. OpenStudio in it's current form requires you to build the geometry zone by zone.