One would be analogous to an ACL arrangement rather than simple ownership. Steam applications could be installed with Steam also having permission to access their resources.

A second possibility would be to have the operating system provide dedicated services for installing and maintaining software. We’re already heading in that direction on some platforms anyway, and it would be useful generally given the kind of security model I suggested. Then software like installers/updaters or package managers can do their jobs in a tightly controlled way, without needing any general access or introducing the accompanying security risks.