Again, if Koei Tecmo was smarter, they would have eventually released a complete edition with all the DLC. That's the only way to keep licensed content (in this case, Mai) from an IP that belongs to another publisher without having to worry about it getting removed for anyone new to the game after the license has run out. That's why we can still play as VF characters, because they're on the discs, they're part of the base game before DLC. I'm glad I'm one of the people who got Mai in DOA5LR, but only for the PS version, which I don't play anymore. I missed out on her on Xbox which is where I mainly play now, not to mention some DLC costumes I really liked. I wish there was something we could do, but there isn't. A petition isn't going to work.
Seriously, KT could have waited until they felt the game was old and dying, and they were just about ready to start working on a new entry from scratch, then release a complete edition. It's easy money, because you would hardly have to add anything more to the game, and it would satisfy anyone who was holding out on buying the game (even with the risk of missing out on the online scene) because they didn't want to have to deal with all the DLC, and I know there's quite a bit of people like that out there (not to mention all the fans who did buy DLC but would still buy a complete version anyways, like me). There had to be a point where their DLC wasn't selling anymore, so the smart thing to do is heavily discount old content and make whatever you can off of it.
Unfortunately it seems they wanted to rush DOA6 out after DOA5LR was barely even considered old yet. There's only one reason why they wouldn't put out a complete edition and that's because they were blinded by greed, preferring any newcomers to the game or holdouts on the DLC to eventually cave and pay the original price, if they even believed or cared that there could be people who want to still play DOA5LR after DOA6's release.
And there's no way they're gonna go back to look at what they can do with DOA5, even if that's the smart thing to do, because they don't even put the game or any of its DLC on sale anymore. That's how much they're neglecting/ignoring it. When we get Capcom sales or Fighting Game sales or Japan-developed or Anime Games sales, you always see Street Fighter 4 and 5 or a bunch of BlazBlue or GG or even DOA6 part of it, but never DOA5LR or its DLC (at least not on Xbox, not sure about PC/PS these days).