>
> (the only way to replace a transaction is Replace-By-Fee but this
> implies the transaction that IS TO BE REPLACED has a certain flag set,
> and it is optional).
>

1. full rbf is becoming standard.   tx without full rbf can just be
rejected as a part of the sabu protocol

2. that's fine.  watchtowers can be used to fix this that only have the
ability to stop attacks in progress.   guarantee transactions can include a
small watchtower fee for your favorite always-on watchtower service

3. all parties need to maintain sabu state (it's just another mempool)