Maybe Carthage could be leveraged until SwiftPM can stand on its own feet?
https://github.com/Carthage/Carthage/pull/1945
Still there‘d be a gap of missing features in SwiftPM to make this the new de-facto standard. Top of mind would be build settings (SR-3948; at least iOS deployment version) and packaging resources (SR-2866).
More nice-to-have features are mentioned in this thread: Swift Package Manager Evolution Ideas