We've been there (although, in case of OT). When implementing CKEditor 5, we started with a linear model and just a couple type of operations (the usual set). At that time, we weren't able to transform that linear model to a tree model because conflict resolution based on that simple set of operations was too dumb. As I mentioned in the other comment about CRDT vs OT, we'd still consider having a linear + tree model duet, but so far it's purely theoretical discussion whether it has a chance to work.