I should also add that the truck sags on the passengers side when driving down the road which is also a possible sign of weak leafs, right? I did not think about swapping the leafs out to coils, and it sounds like it would be a cheaper fix. That or add another leaf? And I think the only reason I haven't taken my truck off-road (other than I've just never went exploring that much with it) is that it has consistently gotten worse over the years.
I can see how people might like this suspension and that it was popular for so many years in production, but for everyday general use, it sucks. As it has aged just like so many others, it sags which makes for an uncomfortable ride. It has never been the pie-in-the-sky ride and leaves me more than frustrated than anything.
In general, if you aren't happy with your stock leaf TTB suspension, the easiest / cheapest fix is to repair what you have, make sure everything is as good as new.
It sounds like you've already done this and "as good as new" isn't good enough for you. The only tried and proven easy fix from there that I'm aware of is a solid axle swap.
As Brad said, swapping to coils would be a custom fab job. Great opportunity for improvements, as long as you're capable of doing it (I don't know that I would be). But not what most would call cheap or easy.
Adding a spring leaf might keep you from bottoming, but the spring rate is pretty stiff already, so no guarantee it will be acceptable with another leaf.
Just getting new replacement springs might be an option. If they are sagging that might be needed to get to "good as new".
I've never looked into lift kits for an F-250 TTB. There might be something out there that gives a little more wheel travel, so that might be worth a little research.
It really comes down to the fact that it's a marginal system to start with. a few people like it, most of us can tolerate it, and a few need to upgrade. If you're in that third group a SAS is probably your best bet.