The ULD container in your screenshot, as the code says, it's an AKH, which is *precisely* what we configured by default to use with all the internally supported A320/A321 and, in fact, is the ONLY ULD that an A320/321 can use so, it's perfectly suited for the airplane, no other type can be used, it is what we configured for those airplanes so, why you said it's for a "larger" aircraft, when it's an ULD made specifically for the smaller Airbuses ?
So no, more "variety" for A319/320/321 would be wrong, since they can only use one kind of container (the one GSX is already configured to use by default on the internally supported A320/321).
Of course, you are free to change the airplane configuration as you like, but it would be unrealistic for such airplanes to use any other ULD than the one we specified for them.