How unique can you get a permit?

Simplified ManagementFor those managing multiple properties, AB 2622 streamlines operations by expanding your hiring pool and removing the red tape often associated with minor repairs.Why It Matters for TenantsTenants also benefit from AB 2622:Faster Maintenance: Minor issues like plumbing or lighting can now be resolved promptly.Fairer Move-Out Costs: Affordable repairs mean tenants aren’t hit with inflated charges for damage beyond normal wear and tear.Things to Keep in MindWhile AB 2622 makes maintenance easier, landlords should still vet unlicensed workers carefully, ensure proper insurance coverage, and remember that jobs requiring permits must involve licensed contractors.AB 2622: A Win-Win for California’s Rental MarketAB 2622 strikes a balance between flexibility and accountability, making it easier for landlords to maintain high-quality rentals while fostering better tenant relationships.

Trouble with cities on permits?

I expect you will need a permit and not be issued one. 

Also if this property is on septic that also can throw a wrench into the ability to call a space "a bedroom" as septic systems are sized and permitted based on the bedrooms.

Insurance- coverage for new engineering, permitting, etc8.  

While this is municipality dependent, if the contractor is not licensed you likely cannot obtain the necessary permits and approvals.

Quote from @Sherry McQuage: Make sure to check the zoning to make sure mobile homes are permitted there; check for any hazardous waste designation for the area; will you need to have the parcels surveyed out in order to sell the size you intend? 

Legal Implications & Ramifications : As an example; the iconic PCH homes in Malibu and many in the upper foothills might not permitted to build back, certainly not to the same extent or materials.

I develop land in Nashville from finding the deals, getting all the entitlement and permits, financing it, to building it in house with my GC license.