Simple feature to allows the combining of tokens ie crafting a 1000 from 2 500s This would also work for shields allowing the crafting of 8, 24, 72 respectively using the lower ones Maybe have a small gold tax for combining shields to keep it balanced
I don't see any reason not to be able to upgrade tokens, but I'm not sure there is enough reason for the revs to put effort into it. The shield concept is different. An 8hr and a 24hr shield are pretty different in function, so that might be a balance issue