SMARTEdTrainer

Try a USB CATx Balun, you should be able to pick one up off the interweb quite cheap. There are different versions for different versions of USB, so just keep that in mind, check its compatible with USB2/3 etc. This unit basically brings the USB plug of your PC to the screen, and then use a 1m patch lead between the balun and the screen. should solve your problem. about embedding it in the wall though? maybe speak to your installers as a snag?

Any Large Format Display (LFD) or interactive LFD will be a much better return on investment, and probably have lower overall cost of ownership than a projector/whiteboard combo. It is a good choice.

I do believe that Promethean have the thinnest glass of the touchscreen manufacturers, as well as a plastic back panel, rather than metal, so if you have concerns over damage, check the MoHS rating and thickness of the glass before deciding on brand loyalty. it really would benefit you to invite all the manufacturers and have a show-down.