Is there really any reason that we can't just do a flat Leppa Berry ban? I remember when this discussion first came up during the time of the initial Endless Battle Clause, there were a handful of people who were adamantly opposed to banning Leppa Berry outright on the grounds that it has legitimate competitive use outside of endless battle strategies, but I have yet to see any real examples where Leppa Berry is the optimal item on a certain set. Nobody actually uses Leppa Berry, and there's a good reason for that. Outside of a few extremely situational circumstances, Leppa Berry will always be outclassed by Leftovers or some other item. Meanwhile, look at what we gain. Rather than trying to band-aid the issue with a handful of complicated bans that very well may be bypassed later on down the road, we can cover all the bases with a simple ban of an item that no one uses competitively in the first place. Not only that, but we can ensure that no further endless battle issues will arise. As far as I know, there's no way to cause endless battles without the Leppa Berry since you or your opponent will eventually die to Struggle; the only ways I know of to keep the opponent alive during Struggle are through Heal Pulse and the Truant + Protect combo mentioned above, and you need Leppa Berry in order to perform either task infinitely.
Ultimately, I think the benefits of simplicity and nipping the problem in the bud far outweigh the microscopic collateral damage of banning what is ultimately a gimmick item in the first place. If we were willing to soft ban a couple of BW Cacturne's moves in order to ban Sand Veil in OU, then I don't see why we can't be equally willing to eliminate a few subpar (and basically nonexistent) Leppa Berry sets in order to take care of endless battles in the most simple and efficient way.
