What do you want to see?
At the moment, Search for Messages (POST channels/{target}/search) utilizes nearly identical parameters to Fetch Messages (GET channels/{target}/messages), but the former uses a JSON request body whereas the latter uses query parameters, which in my personal opinion is a worse way to build requests especially with as many parameters as the methods allow.
Would it be possible to make both endpoints use the same request body type (specifically a JSON request body instead of query parameters) for consistency? This would obviously be a breaking change for clients and API wrappers which depend on this functionality, but I think it would be better to get that over with sooner rather than later.