Water and electronics dont mix... You might get it running now, but over time rust will spread within electrical components and start causing issues all over the place (with a possibility of electrical fire!). So theoretically yes it is possible, practically you need to replace every single electrical component, including insulated ones.
Take it from a person who was involved (directly and indirectly) in post-Sandy recovery efforts...
Hers : 2015 328xi MSport Silver/Red
His : 2016 X3 35i MSport Silver/Mocha