You do realize that I was only kidding?
But still, if you get into the diplomacy of it and taking over other races, then it really is not going to get anywhere, because everyone could theoretically control everything, and debating about it is better. So, I set the limit to 3 to keep it standard and to avoid the "Well, The Altmer are friends with the Bosmer, so I could get them to help." Because then that makes it 4 against 3.
There have to be some standards.
I would chose Orc, Wood elfves, Argonian. Orcs for the combat abillites and power to take less damage and do more in battle, wood elfves for the archery cababilites and the abilty to call animals to help in a battle, argonia for water breathing and natural ablitiles to adapt and regenarte health.
But massing your whole navy to a blockade would negate the Redguards out of the conflict (the Altmer as well). And then tell me how the Nords and the Dunmer will work out their racist conflicts and unite against my Bretons and Orcs? I don't think it "would be a simple matter to conquer High Rock". Except you had more troops in numbers, of course, which might be true or might not be true, I'm not sure lore-wise.
I have a thing for the diagram. The orcs are front liners, right? You can't fire arrows on your own guys, so you should probably use them to strengthen your weakest fighters.
The battlemages' attack will probably not be that effective, and the attack and retreat will just give the enemy time to pick them off.
On the second diagram, you're opening up yourself to be surrounded.
http://www.uesp.net/wiki/Lore:Redguard
They suck as soldiers
Three races... Redguards, Imperials and Orcs. Redguards will form the Vanguard of the attack, armed with Medium Armor, Spears and the like. The Imperials are our Battlemages and healers. Orcs will be the all-around fighter, offense or defense.
I could also replace the Orcs with Khajiit, they make good one-handed soldiers and the Senche-Raht would make great fighters, while Suthays would be agile in Heavy Armor.