Don't get me wrong, I'm for better player loan systems like that and working the partnerships that the super sides have been building, I just don't see it helping the rebels right now. Fundamentally if you want hang onto your locals you just need to sign them first, over the external players.
It is more or less the brumbies system - they focus first on what they have available to them and then augment it with targeted recruitment. It's the more sustainable path for talent importers, but it takes a lot of focus and requires internal development systems to be functioning well enough for players local or imported to realise their potential, otherwise they're better off elsewhere. That's why I think Melbourne should focus on a feeder team setup right now, Dewar Shield isn't up to it but the accelerated development potential in running a couple of feeder teams in the main club comps makes the rebels and competitive and realistic option for young players.
That said it might not be sustainable in the long run, but that's a broader issue for Australian rugby that goes to the need for a formalised 3rd tier.