We're in Israel.
The center is actually a requirement, as far as I'm concerned. In the current apartment the speakers are at a similar angle to the MLP, and I can definitely tell when using stereo vs 5.1. And planning in-walls seems to be out of our budget, both in terms of money and time - the construction needs to begin very soon, otherwise we will delay our move which is bad for multiple reasons (even ignoring everything else, it would at least cost us dearly in rent).
Currently I'm leaning towards making cubbies with the option of closing them off with a door. That way, I can hear how bad it sounds once everything's done, and fall back to moving the speakers out into the room if the sound quality will be unacceptable.