Your writes are always going to return a write model, and that won't account for indexing problems when you don't return an error - so your clients may naively equate a non-error response as a success. If you're the one writing the client, maybe that's not a problem. If you have several consumers who don't know the ins and outs of your system, that might be a very serious problem.

This is the problem with CQRS. The answer to so many of these little tweaks depends on a ton of system knowledge and contracts and promises, and it's really really easy to make the wrong choice.