Can't see scripting helping with map size unfortunately, well not in the sense of tiling it anyway. At first when you start playing with Reloaded, the map size seems huge, but the more you use it and try ideas, the more you realize it is merely large. In fact it only takes a minute or so to get across the whole map, dependent on your speed of course.
Now if you could live with the map looking less smooth, and you could set the scale of your character size, then you could make the current map seem huge. Imagine say you scale down to a dog or cat size, straightaway the map will seem far bigger, go to ant proportions and the map would seem massive. So an ability to do that may help to some degree, but as I say the quality of the terrain would be decreased at the same time.
What I would like to see with the current map at least is the ability to make water stretch onto the horizon. At the minute if you make an island surrounded by water, the edges by the sky box are so glaring it is quite obviously a box. You may be able to get a sky box which matches better, but even then it would still probably look awful. The sky boxes always seem oddly stretched under the water line as well increasing the poor look when glancing out to sea. I include a shot to illustrate.
I'm not so sure that having a larger map would be a huge issue performance wise. Obviously as it is now it would, but if it had some sort of tiling system where it loaded the map in chunks it would work ok. I worked on something like it with a friend a fair few years back in DB, and although the segments were set as such, you could run through a huge map as large as you really wanted. I think we used a 5x5 grid of large terrain chunks and simply worked it like a big 3d Zelda map. Obviously running round an empty map with no collision bar the terrain is not doing so much, but the basic idea worked great at the time. Obviously, not a simple thing to implement here because of the nature of the editor and the map itself, but not impossible as far as I am aware.
SPECS: Q6600 CPU. Nvidia 660GTX. 8 Gig Memory. Win 7.