I've got an idea:
A magless design, simillar to the q-loader setup but with a 10-rd capacity. You reload it by pulling the string and compressing the spring so the feedgate is open for a 10rd tube. This would require turning the marker up side down each time. Also the string would be flying around your wrist.
Let me know what you think guys.
P.S. sketchup model found on the warehouse