It's a good idea! We considered it while we were developing the game. Currently, the balance of the pieces is too delicate to implement something like this (for instance, if you had a relic like "all darkness pieces get +1" it would be way too strong, because 1 point is worth a lot, especially when you get to apply it to many pieces. If we wanted to implement these kinds of effects, we'd have to increase the points of all the pieces to have more fine-grained control. We liked the chunkiness of the small numbers so we decided against adding the passive upgrades. If I made another game like this I might consider designing it to accommodate passive upgrades like many other games in the genre