User blog comment:LurkerLordB/Celtic Union Flags/@comment-90.220.190.160-20140116130116

Actually you can simplify the whole thing. For Britanny, you can use the Kroazh Dû, which is the inverse Cornish Flag, loose the symbols for Wales and Ireland, use a triskele for the Isle of Man, all put together you get :

https://31.media.tumblr.com/a64b867051492b0b877534501050279b/tumblr_mzhw3r9XBi1tphxzko1_1280.png

It doesn't look too much like the Union Flag (we don't want that, do we ?), kinda looks like a Celtic Cross, and incorporates all main elements of the flags.