Hi!
I'm working on a game which is using an isometric perspective. It's kind of possible to apply the tiles with the current grid but very time consuming. Plus having the grid locked at 8px by 8px in the tileset editor is quite restrictive, changing that would already make it a lot easier :)
I think that having an isometric grid is a small feature that would add a lot of possibilities for really cool design. You should think about it.
Thinks 'Terranigma', and smiles, That, or 'Sabrewulf'.