With this image - as badass as it is - you can start to understand why a younger actor had to play Max.
How old does Max look like in this pic? His mid-50s? Yeah he could pull off the look. But it would create a few problems with his character. It would make it about 30 years after he lost his wife and child. That's more than enough time to shake it off IMO.
Because I think past that time there's no turning back - It would be pretty clear that Max would never recover from his tragedy. Most importantly, it creates a problem: suddenly there's no place for his character's arc which has always been (at least since RW) - his return to humanity. Would Max, in his mid-50's still be traumatized by the death of his family? Or maybe the writers would have to replace this tragedy with something else to make more sense and open Max's character up for development?
Now, if - theoretically - we replaced Hardy with Mel it starts to make sense why Max has PTSD flashbacks in FR that involve all kinds of different people - to keep Max's tragedy going because honestly - how long can you milk his personal loss after all those years? I dunno, I'm overthinking this thing again, but hey, just my 2 cents
Great job on the image Danilo Gentili and welcome to the board! Max really looks like a grizzled veteran of the road and that's awesome.
work, thanks for sharing! 
(I wonder why Max lose one of his eyes but I still love this Idea ! )