why do you require a sprite for terrain generation? it seems you could get off just fine by setting the height of each point randomly,
perhaps you could create a value map 1/4th or wtv the size of your required size, set every 4th point to its matching value in the value map, then interpolate for values in between which arent every 4th point using cosine interpolation (cosp) perhaps as a smoothing algorithm between the values that point deals with. it would be complicated, but then again what your trying to do is complicated, i dont quite see the use for a perlin noise plugin unless im missing something, perlin noise is just a random value set with smoothing isnt it?
EDIT: it seems what im describing is simple gradient noise, perlin noise is slightly more complicated in that you would need multiple different resolution value maps and multiply them by each other to create a value set with macro and micro variationshttp://freespace.virgin.net/hugo.elias/ ... perlin.htm
what i said would need to be combined with some of the stuff described on this page, it would leed to realistic terrain and i full confidence it can be done in construct with a few arrays and some complicated eventing