They can be modded back in using the Nova Crystallis mod manager. That can be found on Krisan Thyme's discord server, a link to which can be found on the right side of the FinalFantasyXIII subreddit under discord servers (FNC:ModdingCommunity).

A little late for a reply, but I believe all the DLC garbs are available on PC (Steam) except for 2, and those can be modded back in.

The problem is that each garb is its own model so you would have to alter each one individually.

I am not aware of one, but that doesn't mean one can't be created. https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2816930477

You can look here.

A little late, but here[www.nexusmods.com].

We can pray[i.imgur.com].

A mod is now available on Nexusmods[www.nexusmods.com] that improves many of the textures and models in the game.

Originally posted by Krisan Thyme:

I might need to hit you up on this and ask you how you managed to do this, if you don't mind?

Sure. You can PM me.

I would think the bigger problem would be the physics of the models. Would those be similar between the PS3/PC systems? Typically I've found that if you can find an existing shader in the destination XIII game that takes similar textures maps to the original (or you coerce the map into what it expects), you can get it to render fairly well. That is what was done for porting the LR models into the base XIII game (over on NexusMods[www.nexusmods.com]).