Sling Installer currently always updates bundles when different versions of bundles get installed. Since Apache Felix does support multiple versions of bundles to exist in parallel it should be possible to change the behavior with via property to install and uninstall multiple versions in parallel instead of updating them.
To achieve this two changes are required:
a) DefaultTransformer should change the EntityID of bundles to include the version to make sure the state handling of Installer handles each version as own entity
b) BundleTaskCreator must be adjusted to create install task over update task as the detection currently checks for the existence of BSN