I would advise that for both 4.0 and 5.0 a ping jitter limit system should be implemented. Ping limit alone does not kick for unstable ping. An example, my ping is 150s. If you take a log of my ping you'd probably see a sample data like this:
150, 152, 148, 154, 146 - the average (150) is below the ping limit and fluctuation is minimal
But suppose we have a situation like this:
150, 200, 100, 170, 130 - the average is still 150, and hell these ping results are even half decent in value, but in-game it results in a very inconsistent experience, warps, temporary cut outs and staggering.
Also, there are situations, predominantly in low pingers where you'll see them spike to a high level of ping and maintain that for seconds on end during a fight, then it spikes down to their nominal ping, no kick. I'm talking someone with 70 ping spiking into the 300 to 600s and maintaining that line during the fight, then conveniently drop when the fight is over. Averaging method is not enough to protect against that and it is very annoying to fight these kinds of people.
What I propose is to grab a sample data of a person's ping for a period of time and do a standard deviation check to deduce the jitter. You'd flush that data with each check to keep it fresh, so that you don't drown out any momentary spikes with a large sample of lower values.
This doesn't replace the pinglimit system, that is still needed, this only aims to tackle the quality of the connection which should not be ignored or mistaken to mean being under a ping limit.