I tested out those Hewnsman stairs and they worked fine on the rooftop of the house my sims are living in. I also haven't gotten any more freezes, but now I get lag, lots and lots of lag. A 5 second or so delay on just about every command.
I think I'm going to go see if I can find that Uni super patch.
ETA - I guess the problem with the stairs is when they are stacked together for more than one floor. I didn't test that, so I'll take their word on it.
As it turns out I already have the Uni Superpatch so I can revert back if I want. Going to sleep on it and maybe try again tomorrow before deciding for sure.