Rate proportional to health mechanics
As mentioned on http://forum.freeciv.org/f/viewtopic.php?f=9&t=91059&p=100514, we probably need to decrease attack power of wounded units. CivIV and later have strength proportional to hp, but they also have a mind-blowing system of calculating the firepower, I think we can't just use this part of mechanics for now, so let's concentrate on fire rate. Let's introduce a ruleset setting or a unit type flag that diminish bombardment rate proportional to the hits. While bombarders normally don't suffer damage, some of them do also regular attacks, or can defend against them, and should bear the hp losses negative effects (this is especially useful for the units without "damage slows"). Maybe we also apply the same setting to Combat_Rounds value so that a wounded unit will attack more careful.