Regarding combat attacks.
I'd like to get rid of the problem that units with no legal attack types end up attacking to deal no damage and receive a counterattack. This happens when you try to shoot at a target that has missile (or magic) immunity but is flying and you can't hit flying units either.
An obvious solution is to simply mark invalid attacks as invalid : basically if the unit can't shoot at the target due to immunity, the cursor switches to the red X and clicking does nothing.
However, this is not functionally equivalent. Shooting at the target will add suppression, even if it deals no damage, so shooting at the missile immune unit before attacking is a valid strategy which would disappear.
So I see several possible ways to resolve the problem :
1. We can change the rule to "Invalid ranged attacks (Missile or Magic immunity only) add no suppression". If the attack cannot reach or hurt the target, they won't get distracted by it so their ability to retaliate to melee attacks stays unaffected is a valid justification. In this case, marking the unit as an invalid target is the correct solution and no further action is necessary and obvious downside is losing an existing - but somewhat counter-intuitive and human player only - strategy.
2. Keep everything as is, but mark ranged attacks invalid when invalid melee would be available as the replacement. So you can shoot if you are at least 1 tile away from the enemy, otherwise you can't use either type of attack.
3. Get rid of the "pick melee instead" feature entirely. If ranged attacks are available, always use them, no matter how useless they are.
4. If both melee and ranged are available, open a menu where the player can select which one to use. Otherwise use whatever is available. Ranged on units with immunity count as available. The advantage here is the player also gets control of which attack to use if they otherwise would not, for example on a hero that has both a high melee and ranged attack. The downside is, player has to select what to do so it's slower and opens up a window for mistake (for example an enemy chaos spawn is already next to your row of archers. You'd never want to click "melee" by accident and clicking ranged for each archer is a pain.)
5. Always default to using the ranged attack if available, like 3, but holding Shift can force it to default to melee instead.
I'd like to get rid of the problem that units with no legal attack types end up attacking to deal no damage and receive a counterattack. This happens when you try to shoot at a target that has missile (or magic) immunity but is flying and you can't hit flying units either.
An obvious solution is to simply mark invalid attacks as invalid : basically if the unit can't shoot at the target due to immunity, the cursor switches to the red X and clicking does nothing.
However, this is not functionally equivalent. Shooting at the target will add suppression, even if it deals no damage, so shooting at the missile immune unit before attacking is a valid strategy which would disappear.
So I see several possible ways to resolve the problem :
1. We can change the rule to "Invalid ranged attacks (Missile or Magic immunity only) add no suppression". If the attack cannot reach or hurt the target, they won't get distracted by it so their ability to retaliate to melee attacks stays unaffected is a valid justification. In this case, marking the unit as an invalid target is the correct solution and no further action is necessary and obvious downside is losing an existing - but somewhat counter-intuitive and human player only - strategy.
2. Keep everything as is, but mark ranged attacks invalid when invalid melee would be available as the replacement. So you can shoot if you are at least 1 tile away from the enemy, otherwise you can't use either type of attack.
3. Get rid of the "pick melee instead" feature entirely. If ranged attacks are available, always use them, no matter how useless they are.
4. If both melee and ranged are available, open a menu where the player can select which one to use. Otherwise use whatever is available. Ranged on units with immunity count as available. The advantage here is the player also gets control of which attack to use if they otherwise would not, for example on a hero that has both a high melee and ranged attack. The downside is, player has to select what to do so it's slower and opens up a window for mistake (for example an enemy chaos spawn is already next to your row of archers. You'd never want to click "melee" by accident and clicking ranged for each archer is a pain.)
5. Always default to using the ranged attack if available, like 3, but holding Shift can force it to default to melee instead.