Back in February, Dead or Alive 5 Last Round Game Director Yohei Shimbori laid down the law. "We have to deal with mod issues from an IP holder perspective," he warned prospective modders. "We would like to ask PC users to play our game in a good moral and manner. Otherwise, we won't be able to release a title for PC again." The modding community, naturally, reacted exactly as you would expect: with respectful deference to his wishes.
Just kidding! It actually took about a day, according to Kotaku, for the first DOA5 nude mods to turn up, like this selection from Lustful Illumination (which, in case it actually needs to be clarified, is very not safe for work): topless, bottomless, and fully nude, which includes what must be one mightily uncomfortable piece of string. The site currently only offers nude mods for three DOA5 characters—Marie Rose, Ayane, and Momiji—but I'd be surprised if more aren't on the way.
At the time he put his foot down, it seemed that Shimbori was addressing nude mods specifically, but in a follow-up statement to Eurogamer in March, he and Producer Yosuke Hayashi said, not very helpfully, that it was about "our obligation to protect our characters, as developers, especially because mods created might take on a life of their own out in places we aren't aware of." But they never got around to mentioning what would be tolerated, and some Steam users are claiming that Tecmo is cracking down on more conventional mods providing post-processing effects and new or improved textures. Others, however, say that all the banned mods were actually nude mods; either way, right now nobody seems entirely sure what is and isn't allowed, and that confusion is irking the modding community. One user claims he created a mod to remove Ayane's makeup to make her appear more like she did in DOA2, but he's afraid to post it because he doesn't want to get the boot from Steam.
The bottom line? The DOA5 modding scene might be a ball of confusion, but this much I know for sure: Telling modders not to mess with your game ensures that that's exactly what they'll do. (Though they surely would've done it either way.)