How to plan a wargaming scenario?

[Joe98]

For objectives I try to make them realistic and real world.

Often the game will stick a flag out in the middle of a field and ignore the crossroads in the town,

I am never keen on crossroads or bridges as objectives. In real life you would never make a direct attack on a heavily defended spot.

So, if the objective is 3k behind the bridge, you need to cross the river to reach it. Then the attacker has more flexibility and the defender does not nescessarly know where he will attempt to cross the river.
.