Can I get Legion early and still save the crew?
You can add Legion to your squad through Gibbed before obtaining the IFF. (thanks kalina for the hint).
In my play-through I did not encounter any glitches or ill effects.
However:
- You miss out on some dialog you'd normally get by talking to Legion just after recruiting him
- You might want to remove Legion from your Squad with Gibbed before obtaining the IFF. Nothing game-breaking happens if you don't, just some minor inconsistencies.