Well, for my mod Arthurian : Total War I need to have 20 factions in 5 cultures. How I could do that ?

BRITON CULTURE (ROMAN)
Dyfneint : WRE
Dyfed : ERE
Gwent : WRE Rebels
Llydaw : ERE Rebels
Alcluyd : Goths
Rheged : RomanoBritish
Gododdin : Ostrogoths
Powys : Slavs
Gwynedd :
Ynis Manaw : Berbers
Elmet : Sarmatians
Ebrauc : Roxolani

FRANKISH CULTURE (NOMAD)
Franks : Franks

PICTISH CULTURE (EASTERN)
Fibb : Celts

SAXON CULTURE (BARBARIAN)
Saxons : Saxons
Juts : Burgonds
Angles : Alamans

GAEL CULTURE (CARTHAGINIAN)
Ui Neill : Huns
Dal Riada : Lombards
Mumainha : Sassanids

Is it possible ? I know how to change faction name, but when I replace a faction culture in descr_sm_factions I got a CTD.

Also, can someone tell me how to make playable and 'normal' civs for the Roman Rebels, Ostrogoths, RB and Slavs ?