i think that replacing is a good thing but versions of events that sounds like an even better solution

diffs are a good intermediate for minimising data but they need to be checkpointed and being events they have to be signed by the authors so any protocol involving diffs needs to also consider checkpoints...

hey, there's no reason why checkpoints can't literally be collections of the whole original and it's modification chain, that can be a meta event type that wraps them into a bundle, doesn't require any signatures but it's not an event 

 we already tie replies together, why should this be any different for updates of an event... they are a type of reply from the author, and when you request the original that should pull the revision history until the most recent, and at some point, the relays would say "ok, the composite document is way smaller than the bundle of updates can we have a checkpoint pls" and as the old stuff ages just keep checkpoints with edits on them, same same