I'm not a lawyer, but I know that in the US, an employer is generally free to fire an employee for any reason except being in a
protected class This means that just about everything you mention would be legal except for the manager who wants the accountants to be attractive women. Given precedents, the courts and government agencies are likely to call that sex discrimination even though you could argue that it isn't.
Disability is also a protected class. I would guess that a court would interpret "unable to be Venned" as a disability (though you never know with courts), so employers might not be allowed to fire employees for being unable to be Venned if they can make accommodations for the employees. However, there aren't really many people who can't be Venned (I can only think of underage people, certain pregnancy scenarios, and the Self-Respect scenario), and "I just don't like Venning" probably wouldn't count.
Paying employeees for the time spent Venning would not always matter, but it might if minimum wage or overtime laws come into effect. The existing rules say that time spent changing clothes does not have to be compensated, but time putting on protective gear does. The Supreme Court
ruled in 2014 that protective clothing counts as clothes, not as protective gear, (but unions can bargain to have it count anyway). I would assume that time spent Venning would be like the time spent putting on protective gear and has to be compensated. Again, courts often rule in weird ways so you can never know for sure ahead of time.