I’ve seen some ideas about deign ideas for extra treasure maps, but unsurprisingly, they’re all too good (e.g. using multiples to get double and triple rewards). I was thinking about adding a couple different types of Treasure Maps: Bronze, Silver, Gold, Platinum, Diamond (or whatever) that are craftable in the soulforge. The system of crafting is simple: 10x regular makes 1x Bronze, 10x Bronze makes 1x Silver, 10x SIlver makes 1x Gold, etc. The benefit is Bronze starts with +1 extra turn, Silver starts with +2, Gold starts with +3, etc.
This doesn’t automatically make them game breaking, but does give people an option not to sit around on 10s of thousands of maps for no reason.