I want to mention one other idea that would be useful to have in the BOLT12 spec.
Bundled Payments
The gist is to have an invoice with two distinct preimages and amounts in a single invoice.
The use case is for services that require the prepayment of a mining fee in order for a non-custodian exchange to take place:
- Submarine swaps
- JIT channels
A more detailed description of the proposal can be found here :