Speaker setup help!

Unfortunately, reversing the speaker assignments as you propose would cause sounds which are designed to pan from the front to the rear speakers (e.g. planes flying overhead) to go in reverse -- from rear to front. Similarly, sounds intended to seem to come from the TV itself would come from overhead. These effects would be rather disorienting.

You might want to consider wiring the two speakers which are close to the TV as the fronts, and wire the speakers over the sofa as side surrounds with the associated central speaker as the rear surround. Because of the distance between the front speakers, you should get an additional speaker to use as the front center speaker.

Alternatively, hang the TV on the opposite wall and don't use the TV niche.

My suspicion is that the original owners were planning to put a projection screen on the wall opposite the TV niche, with a projector hanging from the ceiling over the TV. while using only the TV's internal speakers when that was in use. You might want to consider that, too.

And don't forget that you'll need to get a subwoofer.

Perfectly matching the center channel speaker to the other speakers isn't always as critical as it used to be. However, you might check with the company that made your in-ceiling speakers to see what they recommend.

If you have an audio/video receiver which includes a room equalization package like Audyssey, Pioneer's MCACC or Yamaha's YPAO, the equalization flattens the response of all of the speakers and thus makes them sound very similar to one another.