Ever Heard Of KISS (Keep It Simple Stupid)?
3 days away does not make up for a far more complicated system. The whole point of KISS is that simple systems are less prone to failure. The more abrasion and themral cycles a system, endures, the more mechanical parts it has, the more prone to failure it is. You need a one stop stand alone system sucking in only gas and power for insitu fuel production on Mars. You need far more for lunar ice recovery. Like I said before it's testable, and I think we ought to test it to put this issue to rest so that even nontechnical people can understand it.
In addition, if you expect failure from the system rather than designing and testing it to meet requirements you just added even more cost in terms of launches.
Regards,
Mark