If you have guitar effects pedals/stompboxes, there are modules that allow you to use those in your modular setup as well. I don't play guitar but since one of my builds is a Rackbrute 3U (small footprint), I got the Bastl Hendrikson which will allow me to use external stompbox (plural when I get a Electro-Harmonix Tri Parallel Mixer, which will let me connect up to 3 external pedals).
Hendrikson is discontinued but ALM also makes one called ALM006 - S.B.G...just something to consider since you play guitar and may have some effect pedals...or this would give you another reason to buy one :)
JB