I resolve this by allowing the PCs to hire some short-term help, for a flat fee (negotiated like a contact). This individual is one of the archetypes out of the basic rule book, no karma (even if the same guy's been running with the group for a while). He comes in, does the job he was hired to and nothing else. No special tasks can be completed by the hireling. The hireling isn't part of their crew and isn't paid by the J. If in the context of the job, the hireling takes damage, that's fine -- he knew the risks -- but he's not going to throw his life away. After six boxes of damage, the hireling is of the opinion "I am not being paid to die", and retreats or surrenders.
Hirelings do not spend nor do they have Edge.
Hirelings do not, under any circumstances, give any of their gear away. In fact, any gear acquired from the hireling mysteriously disappears very shortly after acquisition.
Hirelings do not negotiate for the team. In fact, due to the amount of roleplaying implied in the role, 'Face' hirelings are not available.
Having such a hireling as a contact is advisable for a team that finds itself consistently short-handed for a run.