Increase Upgrades to 50% of the deck, take out 1 mark, remove all quantum pillars/towers, make their hp to 150, and increase reward to 45 coins or such
This would be far too much, let me explain.
If you have 50% upgrades that means you will win upgraded cards about half as often as you would from false gods, and I am not against that, but if you did that AI5 would have to be beefed up not nerfed. I could destroy AI 5 far far far to easy if this was put in place and the rewards would be too good. You would have to beef up AI 6/false god rewards as well.
The only way you beef Ai5 up is adding more upgrades, and I said I am not against that however if they do one less mark and have 150 HP then I think it would be fair to say you could use rush decks on them all the time. Why is that an issue? Because they would be far more worth while to farm than False gods ever will be.
Now your idea can be done and balanced too if you add one mroe thing to add a challenge. This would most likely deal with the random cards Ai 5 have. There could be a certain card from every element that they would have a certain amount of no matter what, and that might do the trick.
Example
Entropy marked Ai5 would have X numbers of antimatters.
Death AI5 would have X number of bone walls.
Air would have X number of shock waves.
Darkness would have X number of Liquid shadows.
Anything that would make it a harder game overall and harder to swarm but everything else would be random.