switch box degradation?

My father is in the process of having a house built and is having his entertainment room wired for his surround speakers. His current receiver only has two channels of power for surround speakers, and is only stable into a 6-ohm nominal load ( w/ 80W per channel into 8-ohm loads). In order to be somewhat future-proof, he has installed 4 surround speakers (which will work with the new 7.1 surround-side/surround-back formats). To make use of the extra set of surrounds (until my father upgrades to an actual 7.1 system), the electrician/installer is suggesting that he can hook all 4 speakers up to the two surround channels through a switcher box and that there will be a) no damage to the receiver; and b) no sound degradation. Does this sound possible?

It seems to me that the switching box may degrade the signal coming from the two surround channels, and that driving 4 8-ohm speakers in the two channels will drop each channel’s load to 4-ohms, lower than the required 6-ohm minimum. In addition, the two pairs of surrounds will play at the same volume, but will be at different locations relative to the listener (so the resulting perceived volume will be different, and the delay times specified within the receiver based on distance to the listener will be mis-specified, leading to degraded coherency among the rear and side surrounds).

Does anyone have experience with these boxes and how well they perform? Would you suggest leaving one of the pairs idle instead (or manually switching between the two based on movie/music use)? I’m not entirely sure if this electrician/installer has a complete grasp of audio issues, so I wanted to double check!