Most collaborative text editors use CRDTs, OT, or a derivative nowadays. For the most part, the paradigm works fine: changes aren't just "randomly splatted" around the file but appear in their expected causal context. Strange things can happen when paragraphs are deleted or moved around, but this is more of a UI problem than an intrinsic limitation, and I'm not sure what alternative you're thinking of other than locking or throwing up a horrible "pick a version" dialog box.

It's more of a UI/UX problem than a hard limitation. For uses cases that require collaboration with offline editing, the person that last merges might be given a split view to sync their changes.

Again, syntactically possible, semantically harder, but it depends on your use-case plus additional constraints (eg max offline time). Maybe not a fully automatic system, but still very useful.

CRDTs with LLM suggested conflict resolution might just be the thing.

Next best thing is keeping conflicts unresolved, but marked as such as a first-class citizen of the document content (see pijul, jj).