Come on, who hasn't played ME3 multiplayer and thought this would be a good idea?
You have two levels of play - special Ops and Battle.
In special ops you have a team - an N7 team, Salarian STG, Asari Commandoes, Turian Special Forces, Quarian Marines Special Ops, a Krogan Krant, etc vs enemy rank and file in various victory condition based scenarios.
In Battle you have an army and can still use your special forces team, but have squads of grunts of your own. Krogans don't just get Warlords, Battlemasters and their Krants, but get to add Krogan Clan Warriors, various support weapons and options, a tank or two, etc.
Do metal/resin for the various special teams, and do boxed sets and boosters to add more variety.
Do a plastic kit for each faction, Krogan Clan Warriors/Mercenaries, Geth Strike Troopers/Troopers, Human Alliance Troopers, Asari Soldiers/Mercenaries, Turian Soldiers, Reaper Husks/Cannibals, etc.
There are plenty of factions you could use, and you could even throw in the Rachni.
I really just want some 28mm Krogan and Geth. I'm not ashamed to admit it.
This would be a major investment though, both for the licence and to do plastic kits.
Old B5W developer and professional shut in.