When it comes to melee units versus a city, while we often look at damage numbers I found its longevity that's the key to the game. It doesn't matter if a melee unit gets in a powerful hit in the first attack, if it has to immediately retreat on the next round. A unit that can get in 2 or 3 attacks will ultimately be a much more effective city taker.
So with that in mind, I created an excel to help compare the old and new for this proposal. I have attached the excel for those that which to play around with.
I will highlight one example to use the excel. Lets look at a rifleman versus a CS I am thinking of attacking in my current game.
Rifleman with Drill II + CA
Attacker Base CS: The Rifleman has a Base CS of 50.
City Attack CS%: The drill + CA promotions give me a 103% bonus to attack the city.
City Defense CS%: Drill II gives me a +20% bonus. Then rifleman have an innate +20% versus all ranged attacks, and a +15% defense bonus in open terrain.
Damage Reduction %
: City Assault gives me a 33% damage reduction against city attacks as well as the damage I take when doing a melee attack agaisnt them.
Starting Health: Rifleman got a bonus +20 health, so 120.
City CS/City RCS: Set by the city I am attacking.
So in this example, my unit can get in 4 attacks, before its expected that the city would finish the unit off. Since humans tend to want to preserve their units, this means we calculate the damage from 4 attacks as the "overall performance" of the unit, in this case: 149 damage dealt.
Now lets compare it with some other options.
Rifleman with Drill 3:
Rifleman with Proposal Drill 3:
Rifleman with Proposal Drill II + Forlorn Hope
So for this one example, we can see that the proposal Drill III would be significantly more effective than the current Drill III at taking on cities. Forlorn Hope would show a little bit more damage than Drill III, but frankly not so much that I might specialize a lot of units in it. I would probably go Drill III the vast majority of the time, and save Forlorn hope for something like an amphibious unit that doesn't take return fire, or once I've already taken Drill III.
We can also see that this version of Forlorn Hope is roughly equivalent to the current City Assault.