Asking if anyone would/could create a new unit, a Roman Legion "The Lost Legion". With how much fantasy is in 3K, i'd love to see this tale get in even if the time period is off.
Story behind it:
In 50 BCE Crassus led 50,000 men to their demise in a trap by the Parthians. The horse archers picked apart the Roman legions, capturing and conscripting 10,000 of them. All records of the legion are lost until 17 years later the Han Empire employed them in battle.https://www.google.com/amp/s/www.warhistoryonline.com/ancient-history/romans-china-lost-legions-carrhae.html/amp
and some ideas if you care:
unit limit on per faction or army
unique captain or general with legion retinue
elite heavy sword infantry with ranged weapon