Nice, that overlaps nicely with some of my disdain for L402... http introduces domains/ssl/reverse proxies etc and that's a big friction with p2p markets:
https://stacker.news/items/1435085/r/justin_shocknet?commentId=1435245I think some of the concerns you raise boil down more directly to credit vs. Lightning, Cashu just being an implementation of credit. CLINK (and the Lightning.Pub reference server for it) can also be used for credit since it can be used in reverse (for debits).
When using Lightning you're right that there's latency that would make sub-second exchanges impractical without direct peering. CLINK is better at this than Bolt12 since it's not using onion messages that add a slow and fragile round trip, but still the payment itself unless directly channel peered will often exceed the desired time and fee threshold.
The Cashu tokens may be claimable in a disconnect, but if the issuing is offline they're also worthless, so it's not really solving anything. If the service or client goes offline with CLINK, it's literally just request response, no different than an REST API... the receiver would fail to sweep or the sender would fail to emit the referenced transaction. Nothing in limbo.
In your scenario I'd do a hybrid approach with CLINK, a minutes worth of credit with the service which debits a local account per-second, and then the customer can either top-up that credit every minute OR the service sends a debit request to the payer to complete or deny every minute based on the prior minutes debits meeting their criteria.