I agree with everyone else's suggestions.
You need some walk in gates so you can get in and out of the working areas without walking way around or climbing over. (I already know you ain't no spring chicken)
I don't really like that big angled funnel area before the sweep gate--too much room for them to run around in on the big end.
You'll be glad you follow Brute's suggestion about the sliding gate at the squeeze alley, and the cut gate to load from. Work em a few times and cattle remember not-so-good things happen in that headgate and morning of the sale is no time to find they don't want to go thru it again to get loaded.
In the gray/green (I'm colorblind) area (holding pen) you may get by with the posts you want to use, but the blue area of the sweep/funnel/squeeze alley is where you want to use big post, tall posts, planted deep and plenty of them. That's where the wrecks generally happen.

I drew the load chute at an angle because I found my bigger ones had trouble making a 90 deg turn.