Obviously, many things are more readily accomplished in a Scenario than in an Epic Game, however, you can certainly provide the AI with Power and overwhelming Strengths in an Epic Game.
I assume you will have at least one CIV that is only the AI and not playable by a Human in your Epic Game.
Invisible Units have Far Greater Attack Power with lesser settings due to the fact that the Defending Unit cannot see them

The "Sneaky Zombie" in EFZI2 Complete is an example of this. Take care though, invisible units start wars because others can accidentally run into them.
Not only can you set up a situation where the AI Needs a Resource that is only available to them if they go to war and capture a City where it is only available but you can also entice the AI to Attack Cities where the Other CIVs will have Great Power or Strong Units available later.
The AI will go after Cities early when those Cities will be the ones that will gain Great Power later. Remember, the AI "Knows" everything in the Game

The AI is simply going along with the Rules that have been programed so it appears not to know
Auto-produced Units are the Best way to control the AI and its Unit Strengths. Set up Strong Units that YOU control when and how many the AI will have and in how many Cities. Then the AI can focus on building the Other Units you provide for it to build... otherwise the AI will simply build Hordes of the Best Units, leaving out all others. This can be accomplished in an Epic game by having the AI build a Wonder that places an improvement in all cities that requires a specific Resource to directly build that is Not available until later when you want the improvement to start Auto-producing a Powerful Unit. The improvements are there early but do not Auto-produce yet. The same Wonder can be set to place another improvement that is placed in all cities on the same continent that will also Auto-produce units when the required Resource is gained.
The AI will build Wonders from the start of the Game when it is easier. Set the Wonders so they build fast and entice the AI to build the Wonders by the Perks and Units they will gain from the start to later. This is more reliable than hoping the AI will build a Wonder later in game.
One of the Good things about this is that unlike other improvements, pre-placed improvements by a Wonder cannot be Bombarded away. IF the City that builds the Wonder is Captured, the improvements can be directly built and they can be set cheap to build. It is best to also set the Wonder to provide additional Strength for the City where it is located to help prevent that City from being easily captured.
You can provide Hordes of a specific Unit at a particular time for the AI by using the above technique.
Beyond this you can also have another early Wonder that places improvements the same as stated above but that require yet another resource that will be available later than the first pre-placed improvement. The Units this later improvement Auto-produces can be the same units that the first improvements Auto-produce but with another name and they can be set stronger if desired. This doubles the numbers of the same unit at a specific time and or allows an even greater unit to be added to the first, then both are Auto-produced for more power.
The AI loves increased Food and Shields in Water for example so this is something you can use to entice the AI to build a Wonder besides the improvements it provides. The same Wonder can also Start Auto-producing a Unit from the start that the improvement it places will start Auto-producing later.
If you want the AI to build Hordes of a Specific unit, set the unit to have Great Strength in Offense and or Defense and require No support.
Obviously, Faster Units are also something the AI Loves as those units can reach where they are going faster.
You can set Powerful Auto-produced units to be able to use "airports" to go to any of their cities in one turn, then the AI will send most of them to one of their cities close to where the AI wants to attack. The next turn, all of those units come after you

Airports do not have to be set to allow Air Trade to connect buildings, just flag allows Veteran Air Units. Also you do not have to have these "Airports" named Airport. They can be a totally different thing that accomplishes allowing a unit to go from City to City. The Sewers in EFZI2 Complete is an example of this. Note that you can still have regular Airports with or without allowing Air Trade if desired as well.
You can set Powerful Units to be able to Airdrop at great distances. This is strong for the AI and a Player must cover all terrain tiles with a unit to prevent the AI from "airdropping" there. Again, like the Airports, you can name Airdrop something else if desired. In EFZI2 Complete, I call it "Unearthing" for particular Zombies to "Unearth" from any tile

The AI Loves this and uses it well. This is especially strong when you combine this with the Auto-producing improvements that produce units that use "Airlift" and "Airdrop" because the units all go at once.
The AI loves Upgrades because they are generally faster and cheaper than building a new unit. Remember that Cost does not really affect the AI as much as the Unit strengths. IF the AI has a Unit that is strongest yet Very Expensive to build, it will try to build it anyway.
Keep in mind that Hit Points are the Most Powerful setting for strength. A lesser unit with more Hit Points will beat a stronger unit with fewer Hit Points. This is not only due to the unit with more Hit Points having basically more "lives" but also, if not mainly, because it helps avoid the "Random Factors" built into the Game that affect the results of a battle. What this means is IF you want a Unit to almost always Win a Battle, provide it with More Hit Points.
The AI will not use Land Transports or Artillery as a Human will so offset AI Power to rely on Numbers of Units, Airlift, Airdrop, Faster and more powerful Units to balance them against a Human Player especially if you use Lethal Artillery.
Set the AI up with improvements and or Wonders that also ease War Weariness.
Especially as your Game progresses, set the AI to have far more Power to offset the Power the Human Player will have. This is Very important for the end game to maintain a challenge to the end when a Human Player that has played well has almost Won.