It's not uncommon for registration fees in California to be on the higher side, but the UT classification does seem unusual for a Bronco. If you haven't already, reaching out to the California DMV to provide them with the correct vehicle information and ask for a reclassification is a good step...
Maui's availability of land after sugar cane production shut down is a golden opportunity to establish OffRodeo sites. And with places like Poli Poli and Jaws, you've got natural off-roading wonders to explore.
Your enthusiasm and willingness to help make this happen are commendable! This idea...