I don't even think Loki knows how to negotiate in good faith, so 90% of his suggestions revolve around distractions and chaos. Negotiation as a distraction, whilst the rest of the crew sneak up? Pretend to be Bruce to unsettle them, and the rest of the crew sneak up? He can look like Bruce, if need be. Threaten them with some rather nasty things, whilst the rest of the crew sneak up? Don't let Loki get creative with threats unless you like being unsettled.

Alternatively- sure, appear to give them what they want. Give them "Bruce"- or indeed, give them Bruce. Once they're far enough away, take it back. He doesn't like that plan, though, because it's not permanent enough.