Returning to implementation of
"C:\Program Files\Activision\Rome - Total War\RomeTW-BI.exe" -mod:bi/modname
I've got it working for my mod that was previously overwritten onto a different BI installation. Seems to work with minimal editing of the mod files but required folder still seems very big - unless I'm missing something.

Biggest space hog is that all UI folder still seems to be required. ??

As compared to the BI data structure I can omit all models_unit except unique skins etc. which need path in descr_model_battle.txt altered to bi/modname/data..... I seem to be able to omit sprites (no unique sprites), animations and sounds folders; and items folder if descr_items.txt and db are taken out as well. The models_strat 'officer' etc .cas files and textures can go (unless unique then path change in descr_model_strat as above) but the banner textures and .cas are required.

Trying to omit text files (have tried descr_sounds_.. and export_descr_advice) gives culture not recognised errors, as it seems to still be referencing directly to RTW/data for missing text files. This makes me worried that it may be referring to RTW/data for items & sounds folder content and could fall over later when/if it gets to missing BI elements.

Any one else made any progress on this???