Essentially, I don't think you're changing the matchup, and you're adding a 4th color. The mana in the deck for non-green cards is already not great.
I remain skeptical of people who say the mana doesn't support Taiga. Who plays Wasteland besides Shops? If more Wasteland decks pop up then maybe it's time to move off a 4c version but that doesn't seem to be happening right now.
You're still losing to exactly the same strategies, and while Pyroblast is tactically a little better, practically it's the same card
I fundamentally disagree with this point. Tactically, Flusterstorm rarely counter Paradoxical Outcome, Pyroblast often does. If you counter an Outcome you tend to win those games. Yes, Flusterstorm can help you resolve a Stony Silence more often than Pyroblast, but how much more often? They only have 4 FoW and they have to have it when we cast Stony, and we have to have our 1 or 2 of counterspell and a mana up to hit the FoW. Obviously Flusterstorm is better if they have 2 FoW, but it is enough worse against the first Paradoxical/Tinker that wouldn't you rather have it? All this forgetting of course that Pyroblast is quite good against JtMS and Dack Fayden.
You're largely cold to fast Blightsteel
This isn't really true. It is certainly difficult to beat, but you can present enough blocks to chump it once or twice and still kill them if they don't do something else (like Time Walk). I lose way more games to Vault/Key or Tendrils than to Tinker/Robot.
Really, if you want to get to the core of it, it's that to beat Outcome consistently, you either need to have a real wall of disruption which they can't realistically break through (Jeskai), or the ability to clock and disrupt at the same time (Shops, since Mishra's Workshop/Foundry Inspector aren't remotely fair cards).
Are you sure Shops is good against Outcome? The people I know who play Shops regularly are convinced that match-up is abysmal. Jeskai appears to be the best at beating PO. I think my current plan of Red destruction (Grudge/Chewer/Cratermaker) + Pyroblast + Disruption (Thalia, Stony, Chalice, Thorn) is arguably better than what Shops does.
don't think energy flux is great against PO
I stopped bringing it in against them after the first game I landed it. They just waited an extra turn and deployed all their stuff, then cast PO twice, and then won. I realized quickly it doesn't actually hurt them.
Grudge can at least trade 2 for 1 and slow them down, stunting development while you hopefully beat face.
It's not even 2-1 tbh. It can often be both a Time Walk and a Hymn while being a Stone Rain. That's like 6-1, right? Outcome is so dependent on chaining together lots of spells and drawing lots of cards (duh) that knocking out 1/2 pieces of mana with Grudge is functionally better than Stony Silence. I think the plan of Thorn/Thalia/Chalice/Stony backed up by Grudge and Pyroblast is exactly where you want to be.