> trustlessly outsourcing the requirement

Unless I missed something, outsourcing watching the blockchain cannot be called trustless; they need to know what to watch. If your watcher collaborates with your LN-hub, you are doomed.

Here is my get-rich-quick-scheme:

* Setup a big LN hub.

* Setup a LN-watching service

Then for each peer connected to both, I filter those that:

* have a balance with <10% on my side

* have an earlier balance with >90% on my side

* haven't been seen for a week.

For those, I submit the tx of the earlier balance. Sometimes I'll lose a bit but mostly I will gain more.

Profit.

Bitcoin doesn't require weekly check-ins, but Good to know (thanks) - that's a less extreme requirement for Lightning. However, being online wasn't a main pressure for the potential problem of central hubs.

(e.g. the large parked capital requirements acting as a barrier to entry, fees - if bitcoin is to be a low-volume settlement layer - plus people wanting to keep spending money consolidated (i.e. opening as few channels as possible) while still getting the benefit of complete payment connectivity)