Much of this is yet to be designed, but in general, our approach has been to lean towards a relatively layered system. That is to say, that at the lowest level, noms probably won't make a judgement about the trade-off you describe above, but rather provide primitives which allow layers above to more easily take opinionated positions.
In the near-term we'll be paying attention to specific cases that arise, and we'd welcome the opportunity to learn more about those that you may encounter.
This is a question that we've gotten quite a bit. It's our view that there's no magic solution to conflicts. There are logical conflicts in the real world that must be arbitrated.
That said, it's a surprisingly basic thing, but just knowing what changed from party (a) and party (b)'s perspective (relative to their most recently agreed-upon state) is somewhat rare or ad-hoc in existing systems. In noms, you can directly compute exactly how state diverged and apply whatever resolution strategy is suitable.
We have plans for applying default conflict resolution for changes to data-types that - in many cases - will be correct, but in the end, there's no avoiding that correctness can only be defined within a given specific domain.
In the near-term we'll be paying attention to specific cases that arise, and we'd welcome the opportunity to learn more about those that you may encounter.