The battle of Balaclava

It won't be easy, for sure, but at least you can try.
First, Nelson and Treville don't have any place in this mission. You have 4 Artillery generals and we have 4 Artillery pieces.
Second, it is possible to replace at least 2 of your Cav generals.
And, third, all 12 generals should be marshals (or close to that) to remedy somehow the fragile defense.
I don't say it is a guaranteed victory, but in my opinion it will be the best attempt to receive 3 stars for this mission.

You are right, Bismarck on Trevilles place. Nelson stays because he has high battle ability and tactics master. Plan is to put Washington and Bismarck on tanks, Nelson on Armored car, upgrade their health to as much as possible and try again in a month or two when I farm enough medals 

I understand your wish to keep Nelson after such investments , but let's face it: his tactics master is good only for an Artillery unit (and you have better options than Nelson for available Artillery units). For a Cavalry unit it is a double edged sword - you may loose more than you gain. And his high battle ability alone is not enough to command effectively a Cavalry unit. Suvorov has a high battle ability and 3 skills which can be useful for Cavalry. I assume you can receive back a significant amount of medals for Nelson, so you can upgrade Suvorov easily enough (actually you have to upgrade only 3 skills - Plain fighting, Mountain fighting, Inspiration). But probably you are right, and step-by-step approach can save a lot of efforts.

Finished Battle of Balaclava with 3 stars thus finishing the game with perfect score

Karl on assault inf, Massena and Barclay on elite inf, Bismarck and Washington on tanks, Suvorov on armored car, Nelson on Musket cavalry, Sophia and Alex on siege art, Mahmud on rocket, Napoleon on field arty.

I tried dozen of times with my lineup and I got 3 key points and killed all targets but Nikolas, and on the last try I killed almost all enemy units except forts...how? A bit of luck and speed. I swept away through north Italy leaving southern imperial fort and siege arty untouched because they are not a threat. Then spearheaded through Slovenia into Balkans together with allies and succeeded. Tanks are most important because of high health and armour, spearhead with them not with infantry. Equip Washington Bismarck and Suvorov with ambulance and health or armor items and steam roll. Soften up with arty and mop up with infantry. Take northern key point with Suvorov and infantry and allies while you move arty and tanks to Sophia and Nikolas. Keep Nelson and one more musket cav on full health to hold the Italy key point from counter attack and that is it☺ It is important that you join up with your allies as fast as possible that they can absorb damage.