I considered DTEXEC, but I thought it to be limiting. So I followed the SQL agent approach that I found in this discussion;
https://community.automic.com/discussion/4878/how-to-execute-sql-server-data-tools-ssdt-2012-package-synchronously-using-sql-jobUsing this approach I am able to pass dynamic parameters into the SSIS solution, run it synchronously, and when it returns control it queries the SQLServer database to determine the results. If problems exist, the error messages are returned to UC4 as well (so the developer does not have to go find them in the SSIS environment.) I also took advantage of SSIS environment variables for secure credential management.
This type of UC4/SSIS interface however also requires that the developers understand how to code to it. I set this up and got it ready for a major project that has yet to launch, so I don't really have any real world experiences with it yet, other than I've rolled a single application into production as proof-of-concept.