You can see if its cheating if a faction is using a unit its not supposed to have or if units have more men than normal or if a player has too many good units/upgrades. Some more easier to notice than others.
A unit has a small flag for each upgrade but as you cant see what type of upgrade it is (weapon and armour upgrades cheaper than experience) its not gonna be easy to tell if a player really is cheating. Except if playing at lower denarii levels where most people wouldnt buy upgrades anyway.
The host can kick players but only before a battle starts and no one can see if someone is cheating until a battle starts.
I dont know widespread cheating really is (and not always easy to tell) so you have to be careful accusing players of being cheaters just because you lose a battle.
CA turned MP into a mess when they allowed cheating for RTW and all we really can do is to play with people we trust or not play at all and just wait for CA to clear out this mess.
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