Malcolm
We tried starting the top three on Supers and to a certain extent it worked, but the two that were usually walking away with the league didn't like it so we went back to it the norm.
It would be so easy to have the reverse grid option and it CLEARLY would level up leagues. If it means less people are leaving the game, either permanently or going 'offline', why not do it? If you think it's a gimmick you want be advocating using the option will you. ?
If two people did not like it back then, what makes you think they will appreciate it this time? It just seems like you are trying to impose your idea on your whole league (although well within your rights if you are a host), but my point is you could enforce the same without an explicit toggle. You could have gone against the wishes of those two people even back then, in which case they would have left (probably will happen again, in case they do not agree with the reverse qualifying).
As for the second point of levelling up the leagues, there is no CLEAR data that can substantiate your claim. But feel free to take an initiative and enforce it in your league, so that you have something to show for it.
Again as I said before, if the host feels its a QoL improvement and the league agrees with it, it shouldn't be any hassle to post a message on your league wall asking everyone to follow the custom rule. The fact that you ask for a host controlled option, gives me an inkling that there is somewhat of a dissent within your league towards this idea.