Thinking adding armor that could function in adding more build possibilities, like lighter armor increasing dash charges and movement speeds opening up for the smaller to medium weapons with the base armor being a middle ground with heavier armor having incentives on knockback and accelerated health growth.
#Different Armor
flat hedge
muted sphinx
Doesn't heart technically fill that purpose? It kind of is "armor" of our character in a way. I think it would be doable to add different types of hearts to fit the purpose you're suggesting if you have something specific in mind?
Of course, I wouldn't mind more item types but that would also mean would have to add a lot more items for that new slot, and there is risk of overlap with other items
spark knot
These effects are indeed covered by other categories. Artifacts, necklaces, and runes cover the auxilary effects while hearts, as Spugelo mentioned, cover health.