The UE library/marketplace should allow to download of assets without the needing ten different engine versions installed. A lot of them involve static meshes, materials and textures, for which engine version is irrelevant. Allowing this would help developers easier use of legacy assets from the marketplace.
Even for more complex project, having them downloaded and allowing a newer version of UE to extract usable components would be much more useful then the newer UE trying to migrate and older project with tons of errors.