I now have a reliable and working solution using CA DevTest & MongoDB.
I used the MongoDB Java Driver APIs and then wrote custom Java/Beanshell code using DevTest scripted assertion steps. Basically, the flow is to create a MongoDB session, save the session object for reuse in later steps, then query and iterate over results and set the results as DevTest variables. I took the standard web services Excel-based solution and deconstructed this into functional CSVs and imported them into MonogoDB as collections (like tables). I query each collection for things like environment info (host, port, etc.), test cases, test data, request payload (I import Postman collection right into MongoDB, it supports json natively). Each call builds on the previous data, then once i have all the call info i need I make a service call and do the validation, then I log results back to MongoDB. I have an independent service pick up the results from MongoDB and log them where/as needed (helps manage server load for DevTest server and HP ALM, in my case).
The performance is great and this has enabled us to move all our Excel-driven tests into MongoDB and only make changes in the spot needed, vs. across many single files. This approach served as a forcing function to use a standard data format for our tests, which we struggled with using many (diverging) Excel-based files. We can update our MongoDB data independently from our DevTest script and we're now easily able to execute across many different environments by defining new environments and the specific test data needed. Since the solution is fully data-driven, new tests don't require new scripts, they just get added to the CSV and Postman files and once imported into Mongo, they "just work". I build/deploy Suite and Test .mar files to our DevTest server and use CVS to execute Suites on a static schedule, 2x/day, then we use Jenkins + Script + Lisa-Invoke to query/execute individual Test .mar files.
I just wanted to share that it is possible and there are some very big wins going this route.
-Jason