Like others have said, adding blood to the current anime would probably just open the door for criticism to be shoved down its throat since it's now almost entirely targeted towards younger children.
You know where blood would be appropriate? If they made a different anime series.
Word of god, if the Pokemon Company has a large enough adult demographic, they should really create a more adult-themed series (by adult-themed I mean closer to the majority of anime) based more on the manga or even just a BETTER series that takes place in the pokemon world (because even though I enjoyed the earlier seasons of pokemon, it's been downhill for a while with everything going to crap in the new season). How could one create a more adult pokemon anime? Not awful art, not horrible writing, compelling plots, and it could be as simple as that.
-- Ali Al-Karam