Deployments - new module
In large projects you have multiple versions of an application installed in multiple places. It is not like you have one location and it has either old or current version - you have few branches and one already has current version and the other one does not (due to various organisational reasons).
Redmine could track update/version deployments in location/branches.
The change IMHO is not big - you just need to add a module that allows to register various location/branches and then relate it to issues.
It can be done with custom fields but this would be a workaround.
Again - basic idea is that it is mandatory that in big systems rollouts do not occur in the same time.