Yes, parallel, largely unsynchronized play could be implemented in something that takes inspiration from UrW, but it would have to make it very clear when things are synchronized, when they are not, and which "weird" effects are to be expected and has to be accepted as a result of being between synchronization points. There'd inevitably be a bunch of griefers who'd want to prey on others, preferably weaker and unsuspecting, as well as duelists (who'd actually take a risk of being hit back by people who play according to the same rules), and that's an area where lack of synchronization (or, conversely, demand for synchronization) will hit particularly hard.