Personally I'm already a little bit bored with the adventures as they're all basically the same idea, so here's a suggestion for a new type of adventure - economic conquests.
Instead of taking troops and defeating army camp, how about we take resources and have to create a more productive economy than the target island. e.g:
Buy a 'Trader' instead of a gen to transport resources instead of troops.
Simple adventures require taking some resources and building a few wells until we make more water than the island economy
Harder adventures require more expensive buildings to be built.
No transport of goods back to home island, just build a better economy to win.
There are lots of options I can think of on how to implement this, for instance what if we can build a mine on the island and buy the required goods, e.g. build a copper mine and trade the copper for the water. The trade prices would probably have to be fixed on the island as part of the adv setup. This will give a variety of solutions to keep it more interesting.
I've had search and can't find this suggestion being made previously, apologies if it has.