Homeschoolers do NOT have to get a GED, in fact, it's a huge mistake if you do. It says you dropped out instead of homeschooling, so get that idea out of your head. Many colleges accept homeschoolers (and for that matter, so does the military), and have different applications for them, in fact, go to any college website and look at admissions standards. For most it will say that homeschoolers need an ACT or SAT score, a special application, and one or two reference letters.
I would start talking to your parents about homeschooling. I wouldn't use the term unschooling because it's very apparent that your parents would not understand. I would plan very carefully what I wanted to do with my time, what would be learned from it, and present it to them very logically and showing how this pathway is beneficial. You can't appeal to emotions, because it doesn't not show maturity and that is precisely what you would need. Just because you quit school doesn't mean you quit learning! You could learn by yourself, but would you? Do you honestly think you could stay committed to learning without answering to someone else? Would you be willing to start homeschooling with your parents and then prove to them that you are motivated to do this without as much guidance? Knowing that blowing it once would probably get you back in school?
Homeschoolers aren't lazy, and they don't lay around all day. it takes a lot of committment on both the parent's part and the child's part. Especially with unschooling, because the assumption is that you are totally immersed in the world and in life...and learning from that. Lots of activities, lots of social stuff, lots of selfmotivation to read and do and explore without fear of being judged.