Sound's like we're doing the same thing; I am putting in a bathroom in an already finished basement; ceiling height is relatively low as well (about 7 foot from floor to joist). I considered the wall mount option, but given the current waste/drain configuration, it will be more feasible to break up the concrete and re-position the layout that is more efficient.

I currently have a shower that has no drain connection; it simply runs to an adjacent floor drain. The floor drain is connected to a 2" drain pipe, which is obviously too small to accomodate a toilet. So, as you can imagine, the only option to start hammering away at the concrete and replace the current system...I'll be saving a small fortune by doing the grunt work myself.

Dave K