The Revell is the only one without resorting to cutting down the Zvezda, and although Revell got it re engineered from the A320/321, the designer stuffed up big time and still added the little flap track fairings for the double slotted flaps only fitted to the A321 and there is not much commonality between it and the A320/321 kit
So a bit of cutting those extra flap track fairings off, then filling the extra flap bit and sanding it all smooth, just adding to your modelling pleasure.
I can't see why you wouldn't be able to cut down the decals, they seem to be all separate rather than having the windows and name logos all in one, and the emergency exit on an A319 is over that logo on both sides, and it is printed separately as well, seems Ray may have had that in mind when you look at how the decal is done, not sure about regos though, he has done them as N6, and the A319's are N8, but he has done a string of numbers to make up your own, so unless you need a rego with a lot of 8's you should be good.
With the A319 kit, I think they have always had both engine types included.