A basic driving license will allow you to drive a 26,000lb GVWR box truck with an actual length of 34 feet. Is this the right call? It doesn't seem to be a problem, because very few people are buying such large trucks for daily drivers.

The talk about "farm vehicle" is a red herring in this whole thread. Actual farm plates are rare. The significant distinction is cosplayer vs contractor, which happens to be independent of commercial plates.

The right answer is probably charging yearly registration (/road use) fees based on GVWR. This is already common for trailers. There should be a part that scales as the road wear from weight does. I think it's something like the third or fourth power?