I think there needs to be a standardized mercy rule. When I was in Florida it kicked in with a 35 point lead and went back out to standard timing if the lead dropped below 35. Everyone knew how the clock was going to play out and there was no debate nor arguments about .
I am in South Carolina now. We had a team ask for it last year when we were up 21. They got the ball after the half and scored on the first drive. Their head coach still wanted the running clock, the officials wanted the clock to go back to normal timing rules, our head coach just wanted to know what the heck was going on.
When I was in Indiana, we played a team and won 74-6. It was an away game three hours away so we only dressed 30 players. The other team's coach refused the running clock and we ran dive every single play with our worst skill player and it still got out of hand. Without a rule you are asking a head coach to agree to what many feel like is giving up. A lot of guys won't do it because they don't want to quit on the kids or they don't want their community to feel like they gave up on the kids.
I would be open to many different solutions, but I think there needs to be a standard that everyone understands and I think the solution takes has automatic indicators so it's not left to human judgement.