I think this question has crucial importance for us in figuring out how to live sustainably on the land, post-civilization. By local inputs, do you mean recycling what comes from the land (i.e. animals living on the land poop back onto the land), or do you mean importing resources from close by (i.e. the neighborhood cow farmer)? I think that even if the importing happens close by, it still isn't sustainable, because it still creates a net loss of nutrients for the place that the resources are coming from - unless the circle is closed by nutrients going back from point B to point A somehow, like hay going to feed the cattle or something.
Personally, I think the way forward requires abandoning the notion of living permanently in one particular spot, and making that spot provide all of one's food. Permaculture could technically allow this, but it has to be done exactly right to be sustainable in one place forever, and eventually, post-civ, we will have to abandon all the aspects of permaculture that require industrial technologies (at least what can't be scavenged) and (one-way) importation of resources. I think it just makes way more sense - life would be easier - if people moved around the landbase, either seasonally or periodically as resources get used up. In many places, the land just can't support humans living in one spot forever, no matter what we do (absent industrial civilization, of course).
In general I think many aspects of permaculture would be useful, particularly the ones that can be applied to the wider landbase to increase its biodiversity and fecundity. Looking at hunter-gatherer cultures, there is no dividing line between cultivation (horticultural practices of various kinds) and foraging - they are one and the same. As the people travel the landscape, they not only gather from the land but also practice many horticultural techniques, like pruning, weeding, burning, dividing bulbs, etc. Their interaction with the land is reciprocal - a true relationship.
By applying low-intensity, low-tech permacultural techniques over a broader landscape, we could not only make the entire landbase more food-producing, but we would also help to fulfill the responsibility we pretty much all share, of healing the earth.