Staying above MSA means (ATC/airspace permitting) you can route pretty much anywhere. If you then establish on a procedure then fine, once on a procedure then I see no problems descending to the procedural alt.
Our lot do not allow the use of any FMC procedure that is pilot constructed below MSA. We still punch it in as advisory, but are not allowed to follow it either on MAP or LNAV. Raw data rules!