The SH that broke his pecker was a mean SOB even when we got him, he got worse with age for sure.. the lady at the stockyards remembers that bull for his attitude and she sees a few thousand a week.. that was 7 years ago.
We sold the GV bull coming on 2 years ago, also at about 7 years old, he loaded up perfectly gently, 4 hours later he walked off at the stockyards, and came up to my side of his pen to get his ears scratched.. A neighboring bull started bellering at him and he did take exception to that and they had to settle their differences of course.
Yes, you gotta keep your wits about you when you're around them of course, and be alert for things that pizz them off.. but I'm still more concerned about flighty bulls than laid back ones.. Here's a bull I raised and sold to a friend of mine, he's exactly 3 years old.. and he's got a good attitude.
https://www.youtube.com/watch?v=vj3vC0oLJY0
Inbreeding/linebreeding.. yes, there's a difference, but you can work around it pretty easily.. it takes an exceptional cow to make a quality replacement heifer before her 3rd calf.. if those calves are father/daughter matings, you may leave a few pound on the table due to reduced heterosis, but it's not going to be a dealbreaker.. you're shipping them off anyhow... If the calf IS exceptional, you probably want more of those genes in your herd anyhow, that bull was doing something right!
Weight.. yes, this is the biggest problem with older bulls breeding heifers... I'm working around it with having a young bull with his own herd.. he should have more modest birthweights than our main bull and it helps me manage pastures and everything else better having 2 of them... and gives me a backup plan should one fail.