The Scout will be a series hybrid. The 4 cylinder engine will only be charging the batteries, not providing propulsion. If Scout allows us to manually turn on the engine, maybe when the battery is below 75% you should be able to maintain the battery charge level.
If you are only going...
Why would you need 250hp? You really only need about 50 to 100hp generator. I would think a two cylinder generator may even be enough, but using an off the shelf 4 cylinder VW engine would keep costs down and with a 4 cylinder it will likely be quieter than. 2 cylinder.