I'd settle for truth-in-advertising requirements.
How about just mandating that using the word "Unlimited" actually means "Unlimited" without any sort of encumbrance (soft cap, throttle, hard cap), otherwise you have to explicitly state the limitations and not be allowed to use the word "Unlimited" at all in your advertising, period.
I don't care if there's limitations, but don't try to bury them underneath an asterisk. Maybe if consumers actually could find hard information about what they were signing up for, they would be a little more picky about where and how they choose to spend their money.
Given that the ISPs can't even explain how one's usage last month results in some nebulous congestion this month (or last month either for that matter--most customers with "high" usage achieved it by taking advantage of the non-peak hours when traffic is down), I certainly don't see any "truth-in-advertising" on the horizon coming from the ISPs.
"...but ya doesn't hasta call me Johnson!"