Document proposals on solutions to F3 <-> EC divergence

[masih]

As part of #718 concretely document solutions that fully resolve it along with pros and cons and engineering delivery estimates.

[masih]

Discussion with @Kubuxu at standup on approachs:

1. Dynamically reduce the candidate set based on EC to reduce proposal length.
2. Final certificate invalidation (i.e. a Lookback concept but for finality cert)

Approach No. 1 seems more elegant. Specific parameters need more discussion.