Those are some good ideas. I have also been thinking on being able to upgrade the augment itself: Let's imagine the silver atk speed augment gives +20 atk speed at the start of the game. Then, with some meta-upgrades, you would be able to turn that card into a more powerful version.
Right now I'm still optimizing the game and want to add a couple more abilities but after that, I will focus primarily on this rogue-lite topic