there are no good options. the recapture occurs if his business use drops below 50%. you apparently don't have a business but are an employee. even if self-employed, commuting mileage is considered personal not business. while the 179 depreciation would be recapture depreciation
paying rent for use of the vehicle also presents problems. first the rent you pay for commuting would not be deductible. second, he would be renting out personal property. that would require the rental on schedule C. any losses would probably not be allowed since between related parties. any income would be subject to self-employment tax. third, there are restrictions for taking 179 as a non-corporate lessor.
recapture is figured as follows
Recapture of Excess Depreciation
If you used listed property more than 50% in a qualified business use in the year you placed it in service, you must recapture (include in income) excess depreciation in the first year you use it 50% or less. You also increase the ad-justed basis of your property by the same amount.
Excess depreciation is:
1. The depreciation allowable for the property (including any section 179 deduction and special depreciation allowance claimed) for years before the first year you do not use the property predominantly for qualified business use, minus
2. The depreciation that would have been allowable for those years if you had not used the property predominantly for qualified business use in the year you placed it in service.To determine the amount in (2) above, you must refigure the depreciation using the straight line method and the ADS recovery period 5 years)
in the future, there may be a way to avoid this if a new vehicle is acquired. use bonus depreciation rather than 179. bonus is not limited to business income and is not subject to sec 179 recapture if use drops below 50%