Eh, don't you also need to divide the lower window - does it really look like in your picture below with a horizontal "post"?
And not that I'm in any way an expert or even knowledgeable in this, but I think it's more relevant what kind of frame you have, and how you anchor the studs, etc., in it.
Then you would need to get two (?) new windows with the right dimensions. I also think it looks tricky to stack leca in that way without bonding, but if it's just the facade maybe it doesn't matter as much. But anyway - the question is if you can't clad an insulated stud construction with sheet material to plaster on instead of stacking blocks on top of each other in that way.
/A