Interesting thought. I generally write things so that they work without accompaniment. I think that one consideration in favor of guitar is that it leads you to chord changes/base line changes, which keeps something moving. If I am not paying attention, things don't move much chord wise, although it may seem that there's a lot of movement on the scale.
Uncle Jacque, I feel that I am paying for my song about the northern spring in a big way today. just shoveled about eight inches of snow off our front path. She's not a lady, she's a b#*!!
I will also check out the system you mention. Not being able to write out tunes is a real limitation. I am with MMario. If I can sing it to you, tape it, whatever, that works but anything else is out of range at the moment.