Yes. Ownership is correct. I copied the original Imperial Cohort entry for DMB, modifed the roman_infantry_cohortesimperatoria roman_infantry_primacohortesimperatoria, and just changed the "soldier" line in EDU (to match DMB entry). Correct files for DMB are in SPRITES/ROMAN folder, MODELS_UNIT folder, and MODELS_UNIT/TEXTURES folder. Here is what the new DMB entry looks like.

; Roman infantry - Prima Cohors Imperatoria

type roman_infantry_primacohorsimperatoria
skeleton fs_pilum, fs_gladius ; throwing javelin
indiv_range 40
texture seleucid, eb/data/models_unit/textures/unit_roman_first_legion_ii_julii.tga
texture slave, eb/data/models_unit/textures/unit_roman_first_legion_ii_julii.tga
model_flexi_m eb/data/models_unit/Legionary_first_ii_high.cas, 15
model_flexi_m eb/data/models_unit/Legionary_first_ii_med.cas, 30
model_flexi_m eb/data/models_unit/Legionary_first_ii_low.cas, 40
model_flexi eb/data/models_unit/Legionary_first_ii_lowest.cas, max
model_sprite seleucid, 60.0, eb/data/sprites/roman/ebsprite_roman_infantry_legionary_cohort_ii_all.spr
model_sprite slave, 60.0, eb/data/sprites/roman/ebsprite_roman_infantry_legionary_cohort_ii_all.spr
model_tri 400, 0.5f, 0.5f, 0.5f