I think you have a good idea...or at least a fun one. I know next to nothing about tartan design, so take my comments for what they're worth. I'd try to match some of the details of the original medal a bit. For example,

* widen the green strip and add a strip of black going through the middle
* lighten up the background color a bit from the tan toward something with a little more yellow in it
* I'm not sure if the color on the extreme edges is black or brown, so perhaps make the sett a bit larger with that color strip included as well. I think to preserve the order, the strip would go between the two vertical red-white-blue/blue-white-red stripes