Since you are doing something better than the law requires you to do, I think it would be fine if you wanted to create a policy to allow this.

For us, we found many cities were changing their OT 1.5 hours to after 80 hours for their police. Due to turnover and trying to keep up, we changed our policy a year or two ago to also pay OT after 80 hours instead of 86 hours like we used to. 

But to go along with more of what you are asking, we do allow our exempt employees to accrue straight time comp time after 40 hours in a week.