I've been trying to design 500hp EM decks that work for FGs when possible, ...
I like to do the same thing; 320 gold is nice. I modified a deckout deck I use against Lionheart, and it worked perfectly first time out, and I see no reason not to expect it to give a 500hp EM almost every time.
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I still have to see what happens if she gets some creatures before you can PA her Quantum Towers. And I don't know how well the deck would work without the ability to play a PA first turn, if your Stone Towers were unupped. I don't think the rest of the upped cards are crucial, but the shields and the PAs would be next.
First PA is for her Quantum Towers. Second is for your shards. Third is for your Time Factory. Don't play a Time Factory without one, and make sure all three Time Factories are either upped or unupped. Fourth is for Eternity. Then you can PA your Stone Towers. Don't worry about those, you can get by if she steals them. I didn't get a PA for those for a long time, she stole 8 of them, and it was no problem getting to 500 life even though I drew 4 Stone Skins early and had to play the first two with only 60 or so mana. The last heal is for your EM, so pay attention to her card count--if she has fewer than seven cards in hand she could deck out when she has one left.
With the Life mark if things go pear shaped and she gets some nymphs, you might still be okay healing 30 a turn by the end, and she can't hit you with the Siphon LIfe thanks to your shield. Other cards I considered and might add if it looks necessary are more Heals, Nova (unupped) and Lightning Storm (upped, cancels Cloak), but if she doesn't get a first turn cloak, you want to maximize your chance at drawing a PA in your opening hand, which makes the game a cakewalk, so keepind the deck small was a priority.