Does anyone know if there are other arts that use suwari waza (or something like it)?
Yes and no. There are seated techniques, but I haven't seen anything like seiza position anywhere else.
In silat there are some seated techniqes, but they aren't done in a position like seiza. It is almost like sitting halfway indian-style (sorry...not a good description). Also in Kali there we do depak (not sure of spelling) drills to drop from standing to our knees, strike, turn and stand.