Currently, we give Parsec clients full control over the defninition of an "interesting event" for an opaque payload by handing them a functor.
Make this API a lot harder to misuse by only giving a couple of options:
Reach consensus on Opaque payloads seen by supermajority of peers (only on valid blocks)
Reach consensus on all single Opaque payloads
This will be done by replacing the functor by a dumb enum with 2 variants.