You can prepare a mod with 'uneven' teams with an init_match.xml (by this I mean the # of soldiers the team will spawn with. Which is what you want)
This way,
whenever you start a quick-match the teams' percentages are already set up. (Just don't change them in the in-game menu!!! if you change those specific settings in that menu it will affect those values, thereby overriding them.)
The rest you asked about can be done fairly easily.

Below is an example of an init_match.xml I'm using for a wip mod which involves 3+1 factions: (the 4th faction is an "infected / zombie" faction" un-selectable for players, and therefore has more 'soldiers', as well as a different AI plan. The un-selectable part is not handled in this example.)
If you just pop an .xml with code similar to this into your mod's main directory it will load each time a quick-match is started. Don't use this code
exactly as it may not be exactly what you're looking for. The most important line you want to know about is the
capacity_multiplier= etc. What this percentage value yields should be fairly obvious.
Quote:
<commands>
<!-- start_game command: new game menu picks up defaults from here and allows user to override certain settings -->
<command
class="start_game"
vehicles="1"
max_soldiers="150"
player_bot_compensation="2"
xp_multiplier="1.0"
rp_multiplier="1.0"
friendly_fire="0"
base_capture_system="any"
randomize_respawn_items="1">
<faction initial_over_capacity="0" ai_accuracy="0.94" capacity_multiplier="0.12"/>
<faction initial_over_capacity="0" ai_accuracy="0.94" capacity_multiplier="0.36"/>
<faction initial_over_capacity="0" ai_accuracy="0.94" capacity_multiplier="0.24"/>
<faction initial_over_capacity="0" ai_accuracy="0.94" capacity_multiplier="1.0"/>
</command>
<command
class="commander_ai"
faction="0" active="1"
base_defense="0.2"
border_defense="0.2">
</command>
<command
class="commander_ai"
faction="2" active="1"
base_defense="0.3"
border_defense="0.3">
</command>
<command
class="commander_ai"
faction="2" active="1"
base_defense="0.75"
border_defense="0.1">
</command>
<command
class="commander_ai"
faction="3" active="1"
base_defense="0.0"
border_defense="0.0">
</command>
</commands>