Installing 10.6 on any Mac that supports it is straight forward, since it was still the DVD era where the OS install was on a disk, which you can easily make a disk image, copied on a USB thumb drive or external drive to be installed / boot from.
10.7 does not care if it is wiped when you do the 10.6 install. In fact I think the 2011 can go further back to 10.5.