I'm sure it has been considered but it's all about calculated risks and probability.
IE The probability of having an evacuation with a minimal load when the main doors are all unuseable vs. the aircraft being out of trim leading to an incident on take off / landing etc.
Just because passengers haven't been briefed on the operation of an overwing exit, doesn't mean they wouldn't be able to open them.
If there are cabin crew in the one of the over wing seats, then it is not necesary to brief passengers.
tsb