This would be amazing. I completely support this.
It could be as simple as, if you have multiple of the item in your inventory, giving a drop down afterwards. For example, if you select Reiflem Berries to offer to the shrine, it then brings up a picture of the item, so under that picture could appear a drop down menu that defaults to one, but has all the numbers up to the amount you have in your inventory. Just like the drop downs in the quick stock.
I think this would be a great addition for items, and even possibly for eggs.