Send/return module as line input/output ?

Hi,
Is there any reason not to use send/return module as line level input/output ?
As far as, in my case, is not needed the use of both of the two to three fonctions simultaneously, it can merge them in 4 or 6hp.

Why not ?

An effect pedal interface? There's no reason why not, although it's sort of wasteful in that you're planning on making no use of half the module.

Go dig through Ladik's modules...there's some better/cheaper/smaller solutions to this sort of problem in their lineup.