There are a lot of items that are available day-to-day that are not only good for their intended purpose, they are also easily used for other "outside the box" applications
A few examples of items I've found to be good for kiting are Muzzy Extreme Bow Fishing Line makes very good sleeving material. I've used it to sleeve mini-blind cord to make pigtails, bridle attachment points and leader lines for my handles.
I have also used an insulated soft cooler and or duffles for a soft kite bag.
Foldable Wagon makes an excellent field wagon for those that carry more..stuff. This isn't outside the box but it works great.
Coleman tent stakes make great kite stakes. Add a golf ball and you have $2 kite stakes..
Disclaimer. Use safety gear to hold items while drilling or fitting..
A broken guitar string makes a great sleeving tool. Just fold it in half and lock the ends together with a split key ring and/or tape.
What have you found that does the job for you despite being made for something else?