Based on the experience from our company, having only the possibility to link External References via link is not always sufficient. Our documentation is being stored in several places on several sharepoints to which access can be restricted, thus, our users need to request the access to see a given document. That is why we would like to propose to enable the possibility to attach physical files (Excel/Word/PDF) to assets which need to have the external reference linked.
Currently there are no plans to enable the upload of documents directly against as asset. The ability to pull that content into an S3 bucket in similar and then reference it there is possible, but the upload directly is not something we plan to support in the near future.