Replace french window doors with just a window?

We have a French window/doors which we need to replace (approx 1800mm*1500mm). We can't really use it for access as there is quite a drop to the level outside. We also don't want to as there are 2 other sets of French windows we do use which are much more practical. I like the light that the windows bring to the room (it is half covered with a sideboard. My questions are: 1) Do we just replace it with more French windows for ease? 2) Can we just put in a large single window? (Would still want to be able to open it) 3) Should we half block it up and fit a standard sized window (if so, what would the approx cost be - we'd need to pebble dash outside to match again) 4) Are there any other alternative suggestions?