Yeah, carefully designed, on-genre, custom Event Cards would be great.
The biggest problem with the RAW is that you'd end up with the hero getting mobbed by all the minions, and that would be pretty boring. I've played linear commando raid type scenarios before, and have split the board into various zones, where only the zones with heroes in are active. So it would run like a series of mini-scenarios, instead of one big game.
Having a gadget power-up in each zone would help each one be more relevant. Maybe have a timer in each zone, so if the hero doesn't get through it in time, it means the minions in that zone have manged to contact the next zone, so they will become active.