Let me inform you right now that you don't need the Guard ID to use the Salvager. You never did.
It says 'Salvager' explicitly on the ID, yes. That's a leftover from previous incarnations of the ID where the Guard weren't generally intended to fly transports, but some such as myself pushed to get the Salvager on the ID so guard pilots could fly it.
The Salvager is a transport like any other transport that isn't a liner. It's not skirting any rules to have one as a plain Junker IDed sort. And the Gallic Junkers need their own ID; this was the way to go about it that involved the least amount of work for the developers. Saving the developers time is key to getting things done, as Discovery is a big mod with an ambitious, demanding playerbase.
As for Cruisers and up, maybe just ask in the special request to have it as plain old Junker ID.