Following the question on re-fuelling en-route to Mars, I am interested in exploring a mission architecture in which a crew may be offered different options for impromptu mission changes, for example in case they have to abort (definitively or conditionally) the nominal landing on Mars.
Within the re-fueling paradigm (for a discussion on "free-return" option, see Note 1 below), one of the possible options is to re-route to a "depot" where propellant and/or life-support amenities have been pre-positioned. What would be the best locations for such depots? Among the following possibilities (non-exhaustive): Mars low-orbits (MLO), Mars satellites, Mars-Sun libration points, a carrousel of cargos orbiting the Sun near to Mars's orbit, ...
"Best" is understood in terms of maximizing rescuing/recovering success, in particular as dictated by the time and energy needed to move from/to a "coasting" orbit (not necessarily MLO).
Assume for the time being that the delta cost to bring the goods to the different locations is "negligible".
Edit-Note 1: A free-return option would not necessitate re-fueling in principle. However, the round-trip journey can take between 2 years to almost 5 years, the faster the outbound to Mars, the longer the round-trip. This would entail carrying more food and water if such an option is included in the mission.