There's no advantage to having a parallel loop other than being able to mix the dry signal with the effect - but you can do that (probably better) offboard anyway, even with a series loop. The only difference is the theoretically better tone from the dry signal not passing through any solid-state circuitry... but as just about everyone finds, this is totally negated by the bad tone caused by the phase/latency/feedback problems with the crude loop design Mesa use. And which they now appear to be moving away from, finally!
On the 2-channel Rectifiers, you lose nothing at all by removing the parallel loop, just the dry signal leakage. Disconnect the wire that comes from the Send pot from the Mix pot and tape it, and you're done. If you don't plan to put it back you can just snip it, you don't even have to unsolder it. If you want to be really thorough you can move the wire from the middle terminal on the Mix pot to the same one as the remaining wire (or vice versa), but it isn't strictly necessary - without doing this the Mix pot just acts as a slight return level control, but not much.
The footswitch bypass path doesn't go via the mix pot on the 2-channels, so you don't even lose the loop footswitching. On the 3-channels, you do - because the footswitch bypass path is via the dry feed to the mix pot - but you still don't lose the Output and Solo controls.
