Findings on character related mods (face, body, clothes, accessories, tattoos etc):
Lists:
1) Separate lists for different mods are possible.
2) Each list can store more than one type of mods, in the form of different textassets.
IDs:
1) Textassets for different categories have different naming format, e.g. cf_f_swim_XX = swimsuits, ca_f_hand_XX = hand accessories.
2) Each category uses a unique 3-digit number as leading number of the 6-digit IDs, e.g. 209XXX = swimsuits, 360XXX = hand accessories.
3) Changing this 3-digit "category" number doesn't seem to affect loading. Only the name of textasset counts, e.g.
Mod A uses textasset cf_f_swim_07 and a ID 209456, the game loads it.
Mod B uses a textasset cf_f_swim_10 and a ID 9999456, the game also loads it.
4) Same last 3-digits used in the same category create conflicts, e.g. Mod A conflicts with Mod B if both of them are used, because their last 3-digits (456) are the same.
5) Rule 4) does not apply to items under different categories, e.g. Mod C which uses a textasset ca_f_hand_10 and a ID 360456 doesn't conflict with mod A or B.