Yes, you would need to adjust the engine based on ethanol content. That's not a big deal for a manufacturer.
Then you would have to verify that the fuel components are ok with the slightly more corrosive fuel that E85 is. Hoses and such may have to be altered.
Seem like you would need to change oil more often so the on board computer has to be adopted to that too.
All and all, you could make virtually any car adjustable to any ethanol fuel without much/any extra cost.
If you have a correct adjusted E85 engine, you will also get more power.
There are many vehicles that may do well with the existing fuel injection and materials used, running well and with no mechanical problems. Had a 95 BMW 316 that never complained once with E85 and my current Jeep with a I6 4.0 does not seem to complain either.