I have a friend of mine who uses a directional antenna from his wireless AP, pointed right at his primary FOH mix position, and he uses a pair of repeaters on either side of the stage too.
He's used to doing large production events with 10000-100000 people (festivals to football games) and he is very concerned about losing temporary control of his systems.
Now he's not using Mackie all the time, but he has a lot of controls that rely on wifi.... Everything from DMX lighting to big LED video display arrays, it's all controlled via wifi.
He uses 2.4GHz unlicensed spectrum for compatibility and the lack of need for frequency coordination.
I helped him design his system from easily replaceable components, and he keeps a spare set of everything. At one event, he had to deploy all 4 repeaters to get full coverage of an arena, so now he has added 2 more, just in case it ever happens again.
Yes, there are better solutions - you don't have to use 2.4/5GHz, but it sure makes life easier if you are using iPads and other off the shelf tablets and you don't want dongles/radios hanging off of them.
In his situation the biggest concern is not just losing control, it's about someone using his systems as a means of broadcasting propaganda or hate or the like...
Hijacking of a system at a major event could be awesome you know. A person intent on doing so could seize control over a wirelessly controlled mixer (they have to break the encryption, but that's not impossible), using the correct mixer software (and if there are access limits in place, bypass those) then they have to know a channel (frequency) of a wireless mic that they can use for their input. Then they have to overpower the actual mic if it is an FM system (capture effect will let the strongest signal win). It's a lot of steps to make happen, but people have done even more elaborate things, like seizing a satellite =)
For us - our biggest fear is high RF from all the similar devices in our spectrum. Therefore, have the best AP you can get, the stronger signal will usually win - and know a place you can run to that is direct line of sight to reestablish your connection.
Also, use a strong encryption key, don't be like the church I was at for an evaluation where their wifi was wide open and within 1 minute of getting there, I demonstrated how anyone could ruin their service.