I mind the reboot more than the R rating. Given what happened at the end of Hellboy 2 there was potential to take the series in a darker direction for a 3rd film. Liz is told flat out that Hellboy is going to end the world soon and she still brings him back to life. Since she is pregnant with twins at the end this means her own children would have died as a result of the potential apocalypse brought about by Hellboy.
So there was potential for a deeper story and for an R rating without it necessarily having to be super gory and vulgar.
__________________ "I know it's gonna work because it's impossible"-George Lucas
Harbour is great in everything I've seen him in: Quantum of Solace, Revolutionary Road, End of Watch, and, yes, even dat dere Suicide Skwaaaaaad. Haven't seen Stranger Things yet. He'll fill the shoes of Perlman well, but...
...I'd much rather see Del Toro and Ronnie finish off a Hellboy trilogy. The original is still one of my fave comic book movies, and number two is pretty good as well. Visually, it was a masterpiece.
The first got overshadowed by the early-2000's comic book movie era that Blade and then X-Men kicked off in 1998 and 2000. Spider-Man dominated, each title in the original X-men Fox trilogy successively made more money than the title before it, and Marvel still had so much licensed out that their other titles (FF 2005, Daredevil, Punisher) followed the familiar character arcs in their titles, just lighter or darker in tone depending on the character and film rating. Hellboy skipped the origin story and tons of character buildup and dumped audiences in medius rex, much like Burton's Batman 89.
The Golden Army was released in what was, at the time, the biggest comic book movie summer of all-time: Iron Man came out to open the summer first week of May, Incredible Hulk followed around a month after that in June, then Wanted, and, of course, The Dark Knight was released just one week after Hellboy 2 came out in theaters. From there, the MCU flourished and DC started their DCEU.
I say all that to say this: since the comic book movie landscape (and the global box office situation in general) is much different presently than it was in 2008 and especially in 2004, I'd like to see how Hellboy 3 would perform nowadays with a much, much, much stronger international market and comic book movies being in the limelight.