@JECE, it's only possible to arrive at that conclusion if you don't know what PPSC is. I have no idea how you managed to get there.
"only Great Powers who would otherwise face certain elimination have a points incentive in PPSC to jump on the solo bandwagon (because eliminated players receive nothing)."
Take out the 'only' in this sentence and you have a true statement. If a player is going to get eliminated if the game were to continue, they benefit from another player's solo. Including the 'only', however, makes it completely false.
Clearly, anyone who gains more from the enemy solo than from a draw has an incentive to throw, since it gives them more points.
Imagine you are Italy in this game:
gameID=146096. The correct play here in WTA is to hold the stalemate and prevent a French solo. The correct play in PPSC is to take Vienna & Budapest while supporting France into Munich and working towards a French solo, because if the Frenchman solos (with you having taken those two centers) you receive 8921 points, whereas with a three way draw you receive 7777.
Since 34/3 = 11.33, any player with >=12 supply centers gains more in PPSC from letting another player solo than from anything other than a 2-way draw. It's not hard to find situations where that's the case, especially since if someone else is holding a stalemate it is not hard to get to 12 supply centers with a stab on them - the only downside is that that allows the player they were stalemating to solo, but that's not a downside in PPSC - it's a benefit for you!
You say that "the most 'loyal supports' of a solo push are almost invariably microstates reduced to a handful of SC's". I honestly hope that is how you play, only supporting a solo push if you would be eliminated otherwise. However, if you were playing this way in PPSC - holding a stalemate instead of letting another player solo when you had a chance to get >=12 SCs - you were playing contrary to the variant's point reward system and getting a lower reward than you would have gotten if you had thrown the game.
If you believe that the only players who should support a solo should be players who would get eliminated otherwise - I have some great news for you! There's a variant that has precisely that incentive, called WTA. You should try it some time.