Gold has become a real issue since the latest update.
If we had another source of gold, it would mean that it would still be a limiting currency (which is a good thing for gameplay, you don't want everyone to be able to get to max everything quickly), but not to the crippling extent it currently is.
Some suggestions for how another source of gold could be included (options, not necessarily all of these would be needed);
1. Have gold as a reward for the Grand Adventure, instead of just the Hero / Villain adventures
2. Have the summoner's challenge pay out a higher amount of gold
3. Have a small amounts of gold available as an item for purchase in the various Exchange shops
4. Have a gold reward as part of either arena payout
5. Have higher gold payouts in both the free and purchased versions of passholder rewards
If you would like examples of how gold has become an issue, please let me know.