It’s worth mentioning that we do have a new IFC writer in our current FME 2025.1 BETA.
If you’re open to trying the beta, you can access it from our downloads page by clicking the arrow next to the current version. The official release of FME 2025.1 is targeted for early/mid July.
The new IFC Writer is a big improvement on our old one, and should be really helpful in your use case 😊
One caveat is that we don’t generally recommend running production processes on betas.