One aspect to consider linguistically is that the Normans removed the Wessex standard which then allowed the modified Midlands dialects to form the new Middle then Modern English standards. This why we have "wall" and "hard" rather than "waill" and "haird" (West Saxon weall, heard vs...
One of my alternate Englishes used a modified theta to replace thorn. The lower case version dropped down like f and old long s, the upper case had a T replace the inner line/tittle.
Doesn't look quite right tbh.
Incidentally, is it me or did the current Welsh flag used to be slightly different? Could have sworn the green stripe was once a third rather than half. Am I having a Mandela moment! Or just my memory playing tricks on me considering how many alternative union...