I don't think there is an easy way to do this. Other than one item with the charges and then an item for each ability score at each bonus level. At that point though you have a ton of magic items to keep on your character sheet and it will make it a bit cluttered.
I've got some custom magic items that accrue temporary bonuses to attributes until a long rest is taken when they reset to 0
1) Is there a way to let players tick off a pool of resources on an item and have it buff an attribute modifier by 1 accordingly?
2) If not, Is there a way to let players manually override their ability score (so things like skills update on the sheet)?
As best I can tell the answer to both is no
I don't think there is an easy way to do this. Other than one item with the charges and then an item for each ability score at each bonus level. At that point though you have a ton of magic items to keep on your character sheet and it will make it a bit cluttered.
1. Magic Item with Charges
2-4. Str+1, Str+2, Str+3
5-7. Dex+1, Dex+2, Dex+3
etc...