Adding ''objectives'' for Scenarios

I just thought about the idea, about adding nation-specific or team-specific objectives in a game.
If I for example make a WWII Scenario and I want Germany(or overall the Axis) to take Stalingrad and Leningrad rather than immediately try to capture Moscow, then why not reward them if they complete the missions with a few new units or some money to push on?

That may not be the greatest example, but it's nothing I would only use for a WWII Scenario, as it could be used for many other of the Scenarios out there.

As of yet I'm not completely sure what the objectives would be(other than capturing specific cities, perhaps in a limited amount of turns to complete) nor how this would work or how hard it may be to program.

The objectives however, would be completely optional to complete or not, so you won't be punished by the game for not completing an objective you were assigned because it's not possible, or you think you rather focus on something else.

Please leave any suggestions for this, or if it would overall be worthwhile to implement into the game.