I will make the counter argument.

Mutlithulls OD classes are different then dinghy OD classes. We have much more of a tradition of working and racing each other. For example, many sailors started on Hobie 14, moved to 16, an 18 a 20 and perhaps back to a 17. Laser sailors do not have much in common with 505 sailors.

We have one design or Formula NA's in the major classes. Picking a OD boat and running a smaller 20 boat championship for the US Sailing championship duplicates the national scene.

I would say the US multihull championship should be a bring your own boat Handicap regatta in one of three disciplines.
Singlehanded, Doublehanded Sloop and Double handed Spinnaker.
Rotate every year...

The Area Championships would match the format of the National championship (Singlehanded) and winning the regional championship gets you a huge discount on a charter boat for the nationals. (Builders would support the championship just as they do now... since they could drop the spin or jib as needed on most of the boats they buld)

The EU essentially does this now.. CARNAC is a huge event with large handicap starts and is essential a run what ya burng EU championship.