Battles = Danger. That's pretty much the game definition based on existing mechanics. The attacker gains, the defender loses danger. Your suggestion is to create battles that create an exchange of ships and gc via Battle, but have no effect on danger.
And since it is optional who is going to use it. Only a fool would opt in a fleet that wasn't stacked. I can hit other participants and not worry about danger. Why would I opt a non stacked fleet with the potential of being hit and losing while the attacker gains. Even if I ignore and it goes pseudo-skirmish, I lose and the attacker gains without danger.
And before you say, you can evade. Even though you don't list a failure rate, evasion would have to have a failure rate, as evasion and fleeing are the same. The only difference is that the other player has actively chosen to attack.