Yes.
Which is a tad nonsensical, really. The homebrew forum was folded into this one, so they're legit threads to begin with. And, 5e isn't written in a less-ambiguous, technical-manual style like 4e, nor with the lavish rewards for system mastery that drove RAW-obsession in 3.x, so there shouldn't be the defensiveness there was towards the rules of the modern editions. Like the classic game, 5e's rule thrive on rulings and variants.
They seem to me to miss or paper-over the actual problem, even though the OP stated it quite clearly:
The genesis of the problem is clearly in the rules, themselves:
1) Heal from 0.
2) Effectiveness of in-combat healing.
Changing the former would remove the major source of temptation to wait until a PC actually drops to heal him. Just count negative hps and heal from the negative total. Support casters should, at that point, stop intentionally waiting for allies to drop before healing them. A simple fix. But, it does make healing weaker in the grand scheme of things.
Changing the latter would mean making healing more powerful somehow - increasing the die sizes or granting bonuses or allowing HD to be rolled & added, I think, have been suggested. Of course, making anything 'more powerful' is suspicious.
Combining the two, though, might balance out and neatly eliminate the whack-a-mole issue.
Actually, I think the OP solution does fix the problem.
Problem 1: Healers wait until a PC goes down to heal them.
Result/Problem 2: PC who was healed from 0 has low health, and goes down again quickly.
Solutions: Resistance to healing, which will make healing from 0 much less appealing.
Downed PC must make a save to wake up before the fight ends, giving more incentive to keep them from falling in the first place.
So, the OP could probably just implement the second solution, as I think that gives plenty of reason to not let someone go down. The first solution is debatable in its usefulness. Some will like it, because it makes the healing less efficient, which provides a second reason to not let people go down. Some will not like it, because it looks like a way to just drain the party resources more.
Results (From what I can see):
Healing characters will spend a lot more slots on healing, attempting to keep up with the damage output of enemies,
and/or You would see more careful play, as the players know it is much more painful to go down.
The first result reads like a bit of a new problem, because you don't want someone dedicated solely to healing against their will. I just finally managed to break my players of the mind set that they
have to have a healer in the party, rather than what they actually want to play. However, if it follows the second result, it should play much smoother I think.