Many slant loads have escape doors, and many straight loads do not (or not with each stall), so I don't get how that's the issue.

Teaching horses to self load will resolve the problem, regardless of trail style.

all of ours self load,and,self unload,and,we tie them in the trailer.But,we don't go inside with them to do it.I tie them from the dropdown window.Does your trailer not have a window at the head of each stall? or is not open to where you can tie them in from the outside?

the problem is when loading one up alone.obviously,you have to shut the butt bar or gate behind them once loaded.well,sometimes,that's when they can panic and,you're right behind them where you might be run over backwards and trampled when the horse is 'unloading' itself like a locomotive.it takes time and patience and practice to teach a horse to go in a trailer and stand there while you secure the gate or bar behind them.if you have mangers,a couple of treats has helped me out really well in training one.I was  told long ago by the man who sold me my first horse at age 12,not to go in a trailer with a horse.THey may come out,but,you might not.

My horses self load, and the ones we tie, we do it through the window.  I will go on the trailer with any of mine as needed, and I do not worry at all about their behavior, but if a horse is reactive, then I think self loading is the best solution.  When I open the rear door, I tap her butt, say wait, take the butt bar down, then say okay.  She backs off.  I didn't really train that - it has just happened that way.  For the next horse, I open the divider and stand behind it to send her off.  That horse has pulled back twice, although she has been perfect another thousand times, I am still more cautious with her.  Horse three, in the front of the slant, gets that same treatment.  If it's our 3rd horse, I can send her off from outside, but it's often an extra or friend's horse, and if so, I again stand behind the divider, which is a relatively safe position.

I was at Biltmore when a woman was killed in the trailer with her horses, so I've gotten a bit more careful.

For some reason,if one is going to jump goofy,it seems to be when they are on their way back out of the trailer.All at once something comes over them,and,they have to put it in warp speed sometimes to get out.When that has happened with ours,they get about a 30 minute session of going in the trailer,and coming out,going in,coming out,etc.I think you get the picture,because they seem to.

I agree,unloading is the most dangerous time,it seems. we are both always well out of the way of the back door during that time.