Well, he was savage mainly towards Misty and i believe it was thanks to their interactions that he changed as a person and started being more empathetic towards people in general, although it might be difficult to notice that since OS is such a long series and it's a really slow progress when it comes to them gaining each other's trust and respect. Not to mention sometimes that development is more subtle than it should be, but i do think it's there.I don’t get what development he went through to go from savage Ash to whatever he is now. Development usually involves some external force that the character went through that changed them. And nobody can blame it on the years that’s went by since it’s already established he’s immortal. I see no problem with wanting savage Ash back; he was more bearable back then. Unfortunately the writers are content writing him every witch way in correspondence to the current saga.
After their relationship as friends grew, Ash realized that most of the criticisms Misty made was out of worry for his pokémon and Misty understood that he did care for his pokémon, he just needed time to grow as a trainer, which he eventually did.
By the end of the OS, you can see that Ash finally acknowledges Misty as a great friend and he is visibly upset over her departure (even though he doesn't show it in the beggining). That is why when she appears again in the show he is far more nice with her.
He was also savage towards Team Rocket, which i do agree that died down quite a bit, but you can still see it every now and then.
Overall, i wouldn't mind him being more "savage" again, as long as his change in behaviour was justified. I think it would be reasonable if he acted like that towards a villain or a recurrent character that really liked to push his buttons, even more than Misty did.
However, there is no point in making him that way again if they aren't able to actually write ironic jokes that focus on witty dialogue instead of just pure slapstick comedy (and i am not too confident they will be able to pull it off). Otherwise, it would just sound like he is being mean and would serve no comedic purpose.