Yes - that is what I was going to do last year, put it at around 2.5' or maybe even 3' - but now I think 2.5' is a good height. If it wasn't for the Silkies I would just let them be. But those wee silkies give me fits! And that one night I watched Marty just launch herself down from her chosen spot (about 3' high), it just gave me the such a fright! And yet she plunked down to her chosen landing spot and proceeded to lay her egg (crazy hen!).You all know that I am hardly an expert chicken tender, though I do think I did a pretty good job designing the Chicken Palace (a few things I would change if I had to do it over, but not many). So, take this view for what it is worth - just food for thought.
I think some of your jostling is because everyone wants to be on the top roost. So as long as you provide different levels they will always be shifting each other around.
I think 4' is a great height when you have more space - I don't know your dimensions, but from your night pictures it does look like they have to be precision fliers to get down from that height.
So, what I would do, is provide a single shelf lower down. I would probably do around 3' but my guess is Bob would say even lower. Remember I am the one with chickens in the rafters who found a nearly 5' roost an unacceptable alternative!
I would then provide one step up like a crate, or a concrete block, or a tree stump so folk can do the jump up in two goes if they want to.
What I was thinking last night (while I was awake with my RLS) was to put in new nest boxes with the tops at 2.5' along the wall, and roosts/shelves the rest of the way so that there was no fighting. It would be all one height all the way around, and put in the steps at one end so that anyone can hop/flap up that way.
I would still have a 'ground floor' level nest boxes for the Silkies (they like to lay their eggs on the ground floor nest boxes) underneath the top nest boxes. Being awake at night give me too much time to think!
I would want the 'ground floor' boxes to be off the floor a bit (~6") - I would put some hardware cloth at the bottom so that they couldn't dig under or chicks get stuck under there.
Also the 2.5' height would be good for the heavy Brahmas, which I would worry about jumping down.... Even though I am told they can roost up high!
Thoughts?