We had a very similar situation where we had reusable services that needed to be called from different environments like IMS, CICS and TSO batch (Db2), so we would have multiple versions bound with all the different LIs, and then another fetchable would sit on top, determine the environment that you were running in, and call the appropriate fetchable for that environment. I’m checking with the developer that championed the migration to DSNULI to see what experiences they had. From a pure simplification standpoint, it was a clear win.
Update: I did hear back from the person that led the effort. While the focus was on simplification, and they did not specifically performance test, they did not notice any significant difference that would raise concerns in their standard validation testing.