Not utilizing FHIR b/c you think EHRs will (a) consume your proprietary reports, and (b) be a downstream data system seems a big footgun. Additionally, while FHIR isn’t quite right for many research use cases, there are ongoing efforts such as mCODE [0], that use FHIR as a base because it is not proprietary and highly specified.
Maybe your EDC has other awesome characteristics. Based on the interest I’ve seen the FHIR ingestion of REDCap [1] is a winner for research nurse efficiency.