I think PON/PON/POCT is the riskiest strategy because it depends on your opponent POCTing G1 and and throwing G2 (like a greedy bastard). If they don't POCT the first game you're totally screwed. And if they've got HCA and the better record, they likely also have the better team and are therefore less likely to POCT.
In this situation, I'd expect a G1 PON from the opponent (based on the OP's description to the team). So I wouldn't recommend this approach. But for a team in this situation that was expecting a G1 POCT, I'd go for it.
The other thing to do in these games (if you're not doing it already) is to blank and LCD. That can squeeze a little more out of your guys.
OK, I'm done laughing at the Princess Bride references and ready to really think this out ...
I think he's going to go PON in G1 because he already has the better team, HCA and the Ent advantage. He might be a little worried about losing the 60K center, but I doubt it. He was dominating before he got him.
Assuming he wins G1, whether he's being greedy or not, he's going to go PON in G2 because he can possibly win on the road anyway and if he doesn't he's all saved up for G3. Then if there's a G3 he plays POCT.
At least that's what I would do in his position. That way even if I go POCT in G1 and surprise him, he has good Ent advantage the last two games and can go POCT in both.
So then, what's my countermove? It comes down to asking if my best chance is in G1 or G3 to get the second victory. If it's G1 with all those factors against me, then I have to go POCT and hope I win and still have enough to win G2 (no easy feat either). If it's G3, then I'm gonna go PON in G1 and put all the hopes on G3.
One reason the PON, PON, POCT idea works is that I have an injured player who could be back for G2 and/or G3 and that could make a difference somehow.
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Now, a separate question. I have never done blank and LCD. Does this mean not assigning starters either? Just pick tactics and assume he'll go with the best personnel for them?