While some comments made sound good, most are not easily implementable, or won't even work out soon after being added. We also shouldn't encourage players to break the law even further after being jailed.
I read about an idea for a jail warden that watches over those that were jailed and kicks anyone that is AFK timing the sentence. I like that idea at first; however, it would be challenging to get dedicated players, or even enough of them, to baby-sit at the jail all the time. So, again, that wouldn't work out shortly after being a thing.
Our current system works just fine as is, and likely won't be changed any time in the future unless the plugin decides to stop working entirely.