I know this doesn't really fit the description of the Mod, but I was thinking of incorporating 10 new units.
7 Unique Religious Units that appear in the middle ages. 1 for each religion. The most common example is the Crusader for Christianity. All 7 are a little weaker then their "equivilient" during the age, but have a specified role.
Crusader --> Attacking Cities
Mamluk --> Pillaging & countering Crusaders
Zealot --> Defence & countering Mamluk's
Monk --> builds new improvement called "monestary" which acts similar to a forest preserve, and can be built on peaks.
the other 3 I forgot how to spell

but:
Hinduism --> "Skirmish" i.e. attack but not "kill" type unit
Taoism --> Medic-esque
Confucianism --> Minor Great Artist, i.e. spreads culture.
After those 7 are impliment, I will have a "hero" version of all 7, which would be a slight upgrade.
in the Industrial Age, these units upgrade to 1 of 2 units, a "Terrorist" or whatever P.C. term works best and a National Guardsman.
Terrorist = Invisible, Always Hostile "Missile" unit that causes collateral damage.
National Guardsman = weaker infantry, but can "see" the terrorist unit and thus counter attack and eliminate before the unit causes collateral damage.
Lastly a 3rd Modern unit is/was impliment for testing purposes
Special Forces = an upgrade of the Marine, Paratrooper, that can also see and eliminate terrorist threats and thwart rival spies.
When I actually "play" Civ, I have these 10 units, and I am curious what others would suggest for balancing.
Anyway I only bring it up, because a Crime Boss, would fit into the "theme", which is alternative supplimental warfare options.