Proposal: create Map Chests (analogous to Glory chests, Gem Chests, etc).
Currency to open them is of course Treasure Maps (one, ten, or fifty at a time.)
Each chest contains one of the possible resource types obtainable from playing Treasure Maps.
Size of each reward and comparative likelihood of each reward scaled so that the expected return over large number of chests is equal to the expected return of playing a Treasure Map (averaged across all players), multiplied by a fraction.
Fraction TBD of course. I’d be fine with 1/3. Needs to be on the low end because this would be a new “opportunity cost” expense of actually playing Treasure Maps. ie instead of playing for 10 minutes to get the full value of a TM, you’d now be playing for 10 minutes to raise the return you get from a TM from 1/3 to full.