For the giants question yes.

dgdata.zip\lua\sim\AI\AIGlobals.lua

Assuming this file is not locked to the dgdata asset we should be able to mod this.

CitadelUpgradeWeights = {
    # Fortified Structure
    CBuildingHealth01 = {
        Priority = -1,
    },

    CBuildingHealth02 = {
        Priority = -1,
    },

    CBuildingHealth03 = {
        Priority = -1,
    },

    CBuildingHealth04 = {
        Priority = -1,
    },

    # Building Firepower
    CBuildingStrength01 = {
        Priority = -1,
    },

    CBuildingStrength02 = {
        Priority = -1,
    },

    CBuildingStrength03 = {
        Priority = -1,
    },

    CBuildingStrength04 = {
        Priority = -1,
    },

    # Currency
    CGoldIncome01 = {
        Priority = -1,
    },

    CGoldIncome02 = {
        Priority = -1,
    },

    CGoldIncome03 = {
        Priority = -1,
    },

    # Blacksmith
    CTroopStrength01 = {
        Priority = -1,
    },

    CTroopStrength02 = {
        Priority = -1,
    },

    CTroopStrength03 = {
        Priority = -1,
    },

    CTroopStrength04 = {
        Priority = -1,
    },

    # Armory
    CTroopArmor01 = {
        Priority = -1,
    },

    CTroopArmor02 = {
        Priority = -1,
    },

    CTroopArmor03 = {
        Priority = -1,
    },

    CTroopArmor04 = {
        Priority = -1,
    },

    # Experience
    CPortalFrequency01 = {
        Priority = -1,
    },

    CPortalFrequency02 = {
        Priority = -1,
    },

    CPortalFrequency03 = {
        Priority = -1,
    },

    CPortalFrequency04 = {
        Priority = -1,
    },

    # Graveyard
    CDeathPenalty01 = {
        Priority = 3,
    },

    CDeathPenalty02 = {
        Priority = 6,
    },

    CDeathPenalty03 = {
        Priority = 10,
    },

    # Additional troops
    # Priests
    CTroopNumber03 = {
        Priority = -1,
    },

    # Angels
    CTroopNumber05 = {
        Priority = -1,
    },

    # Catapults
    CTroopNumber04 = {
        Priority = -1,  # angels and catapults were switched.
    },

    # Giants
    CTroopNumber06 = {
        Priority = -1,
    },

    CUpgradeStructure01 = {
        Priority = -1,
    },

    CUpgradeStructure02 = {
        Priority = -1,
    },

Not sure what -1 does, but if positive numbers do what you expect them to do then seem like the AI is set to pickup graveyard asap. 

use notepad, notepad++ or scite.

The_hunger,

I have started an Skirmish AI project here: https://forums.demigodthegame.com/369930

I think a full skirmish AI will take input and development by multiple people, but have kicked it off with your mod idea.

You can start from that file and play with the values in the AIglobal file included to see what priority work best.  You might be able to find min/max priorities and at what value it signifigantly affects the AI.

The priority for citidel upgrades compete with item purchase priorities.