i found something interesting while checking the original dlc costumes mk9game inis,ermac_c is composed of player downloadcontentunlocked and player isondiscdlc,while the other ones start out different,with playerdownloadcontent unlocked and player download content id,scorpion_c is 1002,subzero_c is 1003,reptile_c is 1004,mileena_d is 1005,kitana_d is 1006,jade_d is 1007.
they are all numbered after each other,so maybe ermac_c was the first costume dlc ever made,so thats why its structure is so different compared to the rest,as it was very beta of sorts.
we could put other costumes,but we would probably need to edit every reference,which includes packages,which are not hacakable as far to my knowledge.
this maybe also why my npc mod didnt work, because the id part,as i tried it with npc basemale adding the npc prefix just to be safe,and even then it didnt work.(no id used with npc basemale)
so my only guess is that we need to edit the eboot to incorporate the trainer from the 360 version,maybe if we could add custom strings(select+r1 to load shangtsung c,extra costume) we could get not only npcs but also extra costumes.
though it would prbabaly be the 1.01 eboot bin we need to modify,guess ill need help from brianj,the creator of the 360 trainer.