Trust me, they aren't worried about doing it right, they're worried about how much money they can make. Just look what they felt was OK for Deadpool in Origins: Wolverine.
They'll never make an R rated film they want tied into the rest of the PG-13 world. The only R rated Marvel movies so far have been the Blade and Punisher movies and those didn't exactly break box office records. The last Punisher, despite being good IMO, only made a few million. Fox wants hundreds of millions for any X film they make. Big budget films just by their nature of being big budget films need to bring in large amounts of cash to justify the project and that means hitting a PG-13 rating. Until you see an R rated film really break that $100 million box office mark on opening weekend, studios won't back big, expensive R rated films. Dredd would have likely made a LOT more money had it been PG-13. Great film, but the rating just killed it at the box office.
M rated video games don't carry the same stigma an R rated movie has. Call of Duty and Halo are both M and they are some of the best selling game franchises out there. They made an M rated Deapool game and I think that's the closest you'll ever see to a true comic Deadpool being done 'right.' Its a strange thing. An M rated game is probably the 'greater evil' as the M rated acts are usually performed by the players, whereas the R rated acts are only viewed by the audience watching the film. But for whatever reason, society deems R rated films as something to keep kids from, but generally they don't prevent them from getting the M rated games.
And so much of these movies are aimed at kids - the toys, the games, super heroes in general, etc. That's not to say they won't have more mature themes or plots, but they aren't going to be spewing blood all over the placee, dropping F bombs, and prancing around naked like they would in an R rated film.
I personally don't know enough about Deadpool to really care if he gets a PG-13 or R rated film, but logistically, I just don't ever see an R rated film happening due to the lower box office intake. Simple as that.
