Updates:
- Opened a feedback report
- Contacted the author of SE-0403: Package Manager Mixed Language Target Support to see if that may help with this.
The team I'm working with did some experiments to work around this challenge. We introduced Swift protocols that hide the Swift framework symbols. These wrappers seem really invasive to our core architecture so we are considering pivoting to using separate Xcode targets, rather than Swift Packages, to break up our code (part of modularization effort).