A few comments on my side (a bit late, but I'm catching up!):
5) Range, Accuracy, Damage, Damage Limit, and Maximum Targets are currently undevelopable from promos and unitcombats (except for those things which currently work to develop collateral since that's how many of these values are derived.)
Proposed Solution: Make it possible for promos and unitcombats to manipulate these values - this can mean a whole new world of development for Siege and Air unit (since Air units use this mission too) promotion lines. They need some more to work with I think.
Not directly related to this project, but I feel the current promotion system (especially with fight or flee) is too overwhelming to be really useful; if there are even more promotions, I'm afraid they will just add to the long list of promotions I never use... I don't know if I'm the only one, but the difference between most promotions appears too minor to be worth the effort - do I want +10% str or +1 first strike? removing xp cap from animals or barbarians? etc. - that I always pick the same ones.
This is a bit OOT here though, so I'll develop on that in another topic later on.
6) When Ranged Bombarding from a city to strike at approaching units, the accuracy odds are greatly diminished. This again seems terribly counter-intuitive and irrational but was apparently done for gamebalance in light of an overly powerful automatic bombard reaction on another option. THAT option has been rebalanced so as to be much less powerful so I believe we can now dispense with this illogical odds hit when bombarding at units from the comfort of a city. (If anything it should be easier to hit approaching attackers as you would have your terrain very well mapped out.)
Proposed Solution: Simply disable the penalty here. I could see Tower buildings actually generating a local Accuracy (and maybe range?) bonus for local Ranged Bombarding units. I wasn't planning on inserting this capability right away but I'll see what y'all say on that.
I feel the current combat system is greatly biased in favor of defense, particularly regarding city invasion. I'm thus not a great fan of giving more possibilities for a city to defend; a walled city with damages on nearby units is already quite hard to take, if it's able to bombard stacks from inside, it will become nearly invincible...
OK, once again that's a broader subject than just bombardment (and the way it works now seems to be unintended rather than a feature), maybe the answer is in removing the penalty while rebalancing something else, but simply removing the penalty without changing anything else would not be a good thing IMHO.
My suggestion:
- Remove the possibility to bombard from inside a city from all siege units (catapult, cannon, etc.) as well as ships. This would probably make sense from a historical point of view by the way - those units need a large space to be handled properly, something that is usually lacking inside a city's walls. Also, even though city fortifications could include some bombardment elements, one could argue this is already represented through the defense bonus (increased damage done to attacking units) and the area damage bonus (spike traps, etc. - there could also be some arrow bombardment buildings).
- For the other units (archers, riflemen...), either also remove it, or maintain it but significantly lower their defensive capabilities. Their defense (including first strike) already represent the capacity of these units to take advantage of their long range to damage incoming enemies, now that this bombard capacity is implemented, they would really become overpowered.
Currently, they are units that are very hard to dispatch, but not that great in attack - great potential for synergies with other units, but not outstanding by themselves: they stand their ground (particularly in cities), but if you don't attack them, they are not a threat to nearby units.
With added bombardment, they would become both hard to dispatch and dangerous for units around them - no weak point!
My personal preference would be to remove at minimum the base city defense bonus (including available city defense promotions) from these units if we let them keep the bombard option from inside cities.
Or, for a wholly different approach, allow only a limited number of units "inside" a city - any number of units may be on a city square, but only, say, size/4 units (or another combination based on unit size with Size Matters) get the defensive bonus of the city (including wall protection), and they are attacked last - thus you can't stockpile large amount of units (especially with bombardment) inside a city.