Could all of the second stages be drifted into a "salvage yard" orbit and maybe station keep for a while? Obviously not launches with different inclinations than the salvage yard, but launches to the ISS perhaps? What sort of device/equipment would be needed at the salvage yard to attach and lock the orbiting stages into formation? Do the second stages fall within the 50 ton down mass limit? Seems I recall they mass less than half of that.
Why do you want to salvage them? Assuming the BFR becomes operational with its extreme payload capability, what possible use could they have?
If the BFR doesn't have a LAS, F9 would be needed for manned NASA flights.
Two things:
- BFR/BFS won't visit the ISS, regardless of the notional image shown during the 2017 IAC, given that BFR/
BFS will only just be coming online by the time ISS is retired (courtesy of real-time taking precedence over Elon-time).
- All NASA manned spaceflight, beyond ISS, is BEO and will therefore fly on SLS/Orion, not BFR. US Congress will see to that.
So, BFR/BFS (supposedly) not having a LAS is not going to present a problem IMO.