1. Tile X & Y separately, yes I'll see what can be done for the next update, but no promises - I have a huge pile of things to get through.
2. IMO the default should really be extended + 0 alpha when using normal alpha blending, black zero alpha with premultiplied alpha. i.e. transparent in both cases. Otherwise with extend you get an unwanted extended filtering with normal sprites, eg. a circle with pixel data touching the edge will appear to be filtered a tiny bit outside bounds. I keep meaning to update this, but worry about breaking existing sprites.
The primary concern is always backwards compatibility over anything else, and the fact that there isn't any guaranteed way to perform versioning properly, I really worry about changing a default. I'll have a think about a suitable solution to this.