I have been using Illustrator for quite some time, and I can't believe they haven't built in a modulated stroke function. Something where you can make a line start at one thickness and then end at another, and adjust it in between just they way you adjust a gradient. It seems so basic. Currently I believe the only way to do this is make a brush then apply it to your shape, but then it's not adjustable. I hope someone from Adobe reads this. It would come in handy for a lot of logos I design.