Cancel buff
I'm sure we've all had some well meaning person come and stick a platter on a building we were about to get basketted which is annoying since you have to wait 45 minutes so adding in the ability to cancel either friend only or both friend and self cast buffs on the building. The penalty for this is that your losing whatever time is remaining.
Dismiss troops
At the moment the only way to lose troops you no longer want is to get them killed which is easy enough (other than the 2 or 4 hour recovery time on attack your making purely to lose troops) when your taking over the island but much harder when you've taken the island as you'd have to purposefully start an adventure which is more than a minor inconvience, so the ability to dismiss a unit (weapons used to make and brew is not returned which would be the penalty/cost) to regain the settler to then train him again for the unit you want would make life much easier.