Hmm, in the end if we use MSC to add deployers as a msc service - we need a listener anyway to wait until all of them are installed? Otherwise it would be just adding the constructed deployers without any injections.
Where the latter would actually prevent people doing weird injections. However i'm not quite convinced that this makes much sense and deployers can be fully isolated from other subsystems. At least if you look at the way common EE injection is currently - where you would need something like a injection resolver (or similar) to set the correct dependencies before you install the services in a deployment. At least i would like to avoid passing "services" through the deployers attachment system.