SF did a lot of SR for XVIII Airborne Corps in the first Gulf War."Such a thing" will not normally work for a brigade commander. There are often unity of effort and unity of command issues when using SOF forces, especially highly specialized ones, in support of smaller conventional units.
These entities, and SOF in general, are finite given their specialized nature. These forces may be available in a small contingency operation but will be harder to come by in a large scale conflict because of operational requirements and priorities of effort. This is why we have SIGINT and HUMINT assets in every service for example.
Theater Commander will have a lot of say when SOF Taskings are levied.