Works absolutely perfectly, thanks a lot :D!
I would suggest though if possible, to list in one of the plugins that 'KEN_TiledFlagsLayer' should be before 'AEL_TilesetPropertyRegions', otherwise it results in an error/crash.
Because it was new I added it initially below, and double-triple checked that the tileset itself was setup correctly before considering the plugin order.
That is strange.
Ahhh sorry, looking back between your new example and everything I was able to work it out after checking more things. The original 'working' wasn't working first of all xD; it was a left over layer from the original method of creating a region map matching the property regions, the one thing I forgot to check.
Removing that meant the bush I thought was working, obviously wasn't because as you say AEL_TilesetPropertyRegions had to actually be before it.
What I missed was the 'Tileset Name' property in KEN_TiledFlagsLayer. Renaming that fixed everything :)!