I'm makign an Mid Sized RPG just to kill time these days and was wandering... Can a map be made useing "all" of the terrain types? If so, why hasn't it been implimented into an Editor like SCMDRAFT 2, etc. And if not, then blow me away with ur simplest reasons.

It cannot be made because starcraft can only load one tileset at once, I think.
Maybe some modder can say that reason, but I saw enough of these ideas before and the answer was always: no.

Maybe it's just me, but I think this is one of those things where,
if it could've been done, it would've been done already.

Can't be done. This has been posted so many times but I will explain it once again.

Every individual tile in a tileset is represented as a numerical value. All those numerical values have different meanings depending on what tileset you are working on. If you are on Jungle, '602' could represent a patch of dirt whereas if you are using Ash World, '602' could correspond to a lava tile.

You could MODIFY the game files to add terrain from different tilesets into a single tileset, however even then the space you have is very limited, and you could not fit every tile from even two different tilesets into a single tileset.

thats starcraft for you...

That statement is ignorant. Even in Warcraft 3 you were limited in the tiles you could use, and you will no doubt be limited in SC2 as well.

Maybe Blizzard will be nice!

If you still hand out precious money for Starcraft II, they really couldn't care less.

Otherwise they'd probably be happy to oblige.