The Federal Tax Credit is actually coming out of the Federal Highway funds, so there is less money there to tap into when it comes to road work (of all types). Thus residents of the 13 CARB states are having tax dollars shifted without regard to the overall highway infrastructure.
Shipping a car in from another State has more than just tax implications. There is also the question of service - dealerships in states where a car isn't sold aren't likely to be able to properly fix one that comes in simply because they haven't had the necessary training. Thus my proposal includes "and service."
Also, did you notice I didn't specify a battery size. If a company can build an EV that gets 50 miles/KWh then they only need a 1 KWh battery. My Volt has an 18.4 KWh battery for 53 miles. Based on published data, I think the Clarity PHEV has a 17.8 KWh battery for 47 miles. The policy needs to be aimed at road results, not battery size. Road results are heavily influenced by drive train design. (AAA estimates that the 95% point for round trip commutes is between 45 and 50 miles.)
Secondary proposal - drop all subsidies from Oil & Gas companies and watch gas prices shoot up. EVs will sell then as well. Either method will eliminate the tilt towards oil/diesel private transportation. The decline of sedan sales since 2012 has tracked almost exactly with the decline of the retail price of gasoline.
2018 Honda Clarity Touring PHEV - Forest Green w/Tan interior (wife's car)
2017 Volt LT - Heather Gray; black bow ties, Charcoal VoltShelf
2012 Cruze ECO MT (hail totaled 5/8/17 103,600 miles @42.5 MPG)
2010 Mit Lancer GT MT (traded for ECO @31K miles)
2002 Pont Montana AWD - title to son at college graduation
1990 Pont Transport (traded for Montana @240K miles)
1986 Fiero GT MT (traded for Transport - needed more seats)
1985 Fiero 2M4 MT (traded for Fiero GT @8K miles)