I just got the combo, and I'm trying to work out the wiring for my setup:

Randall RM4
Digitech GSP1101

For now, the GSP is going to handle effects, and if possible I'd like to leave loops open in the event I get some quality/unique pedals, so flexibility in the setup is important.

The setup I was thinking of is:

Loop 1: open
Loop 2: open
Loop 3:GSP preamp effects (dist/OD, wah)
Loop 4:RM4 preamp
Loop 5:open
Loop 6:open
Loop 7:GSP effects loop for reverbs, delays, etc.
Loop 8:RM4 FX return

So I would just need to connect the inputs and outputs of the open loops to maintain the signal chain and have them set to globally on for now, correct?

It would likely be best to just skip the unused loops all together for now and just route the instrument signal directly to the In of the first GCX Loop you are actually using for the front end effects and run the FX Send directly to the In of the first GCX Loop you are using for the line level effects.

I hope that helps!

That makes sense for making the setup really easy, but wouldn't it be a pain to reprogram all of my patches if I wanted to add something to the setup in other loops?

Any time you add more gear to your rig, you will have to re-program any patches that should activate the newest addition... the audio connections will not change this.