I think the Wario games could go for an M rating. An M rated 3D Wario Land like Conker's Bad Fur Day would be cool. An M rated Wario Ware would also be pretty entertaining.

Dam scalpers.

Like I said...which category are you falling into here...the high brow version...or the low brow?  That's the difference between a movie audience and a gaming audience...and particularly for the vulnerable, forming brains of our youth. This is why I love Nintendo and Nintendo's audience.  They tend to not cater to obsessions with torture.

It's not one or the other though, low-brow stuff can often be high-brow when examined, or at the very least is entertaining, which is far from a bad quality to have. No matter how much you slice it, it's very hard to make certain forms of "high brow" art without indulging in some of the things that make mature themes tick. Sure, there are times where you can communicate mature themes without violence, sex, or nudity, very often infact. But if you wanted to make a game in particular, allowing yourself the freedom of choice as a developer opens up new avenues for exploring certain themes in certain ways. Also, while I agree with what you said about Nintendo's audience, divulging too much from ANY sort of maturity could be considered low brow. 

Fire Emblem is the one non-members rated IP that has the potential to do some with that rating from a story stand point and maybe some risqué scenes if they really wanted.

That being said Eternal Darkness and their vague ownership of the Fatal Frame franchise are still what I would prefer over a franchise being forced into a higher rating.

Also Bayonetta but they don't own that IP...

Wasn't Disaster Day of Crisis Pegi 16?

Not really sure I understand this last part.  But my main point is that for me I don't like when games go "mature" because I feel like the gaming audience (because of the entry age) is more vulnerable than a typical movie audience.  I also think it's one thing to see a character do something and another entirely to take part in that action.  Every child is different and some are better at separating reality from fantasy.  Personally I think that things you watch in movies though they may be obviously fake still send information subconsciously to your brain that creates the impression that you really witnessed (or commited in terms of gameplay) the act being seen.  It's subconscious, mind you, but it's difficult to measure the impact this has on a developing brain.  As an adult I still look away from violent scenes.  I don't need to see that. I don't need to be desensitized to ultraviolence.  

Ok, I honestly don't care about any of what you just said, but that's me personally. I think Retro Studios doing a mature game would be cool.

Also that's not the word I meant to use I meant to say, steering away too much, or rather avoiding mature themes

I mean, they could always pull a persona (12+ in japan M in US and 15+ everywhere else), especially in the case of fire emblem, more specifically an FE4 remake.