A lot of great ideas so far, I agree with most of them, however it may be easier to weigh options when playing (and possibly to balance) if each weapon type is feasible on its own.
Limiting to 3 main weapon lines, I'd offer the suggestion of changing fighters and adding long-range in place of direct-planet.
The rules of long-range could be:
- Does not fire the turn it arrives in-system.
- Targets planets in-system: higher damage vs short-range, loss of pop/buildings once shields drop
- Targets ships within a defined uu range (min and max), damage lands the following turn if ship is still within range.
- Can not target Fighters or block supply
Rough idea vs ships, tracking incoming fire between turns sounds expensive.
Alternative might be to keep to in-system, but delay short-range and fighters by an extra combat round (increasing default rounds).
(With 5 rounds: Long-range fires on round 1, long and short-range on round 2, all on round 3)
The three lines wrt planets:
- Short-range: no change - moderate shield/defense damage, no troop/pop/building damage.
- Long-range: moderate/high shield/defense damage, percentage of population/buildings lost if shields deplete.
- Carrier/Fighter: Low reduction in shields, defense, troops, and some collateral population. Shields do not prevent others receiving damage.
None of the weapon lines could completely de-populate a planet/cause ownership loss.
These would remain the field of invading, bombarding, or other action.
As to removing the 1 turn delay for fighters, I think it helps distinguish them as shorter range weapons.
Not hard sold on that opinion though, and would favor trying Combat Air Patrols.
Flak could (functionally) be an anti-fighter shield type.
(Think flak has been modernly termed for both the cannon and the ammo/discharge type)