While looking back through your various posts on High Valyrian I noted that you seemed to feel that the use of written English to represent the Common Tongue was a case of the production team chickening out: may I please ask if you have any thoughts on what the Common script (“the Common Hand”?) could have looked like?
First, let me say that I actually created the ancestor of the Common Tongue for the GoT prequel The Long Night that got canceled. In the show, it was understood that 90% of the characters were speaking the Old Tongue, with a small percentage speaking the True Tongue (the language of the children of the forest), and the Essosi invaders speaking Andalish—the mother language of the Common Tongue. As a result, it was the Old Tongue that was going to be rendered as English on the show, which meant an Andalish language needed to be created. We produced a pilot for the show, so I actually did all the work; it just didn't come to pass.
My aim with the language was to honor what I thought GRRM was doing with all the various Westerosi names, and with the Common Tongue generally. Specifically, he wanted English but not English. So names like Lannister and Tarth and Tully—these all sound like great English names; they just don't happen to exist. My goal, then, was to create a language which, had the Great Vowel Shift and other English sound changes been applied to it, would produce a language that sounded a whole lot like Shakespeare's English. And so that's what I did. Andalish, as I created, had a very similar phonology to Old English, and I built it out in such a way that had I applied sound changes to it, you would've gotten names like Lannister and Tully and Tarth and all that.
Going along with it, I would have created a writing system that felt a lot like written English. It ultimately would've derived from Valyrian glyphs, but would evolved into a nice, tidy alphabet that had shapes that felt right at home for English speakers. I probably would've found a way to give it upper and lower case, too, even though the evolution of that phenomenon is a bit of an accident.
In all honesty, we could probably do that now, and just create the alphabet the Common Tongue might have. We might not have all the steps necessary (really, we should see what the daughter languages of Valyrian do with Valyrian glyphs, and then base it off that), but we could produce something not too far off, I think. I wonder if I could convince the show runners to use it... lol Probably not, as the only time you really see writing in focus, they want viewers to be able to read it, and the conceit is that while we're hearing English, they're actually speaking the Common Tongue, and the same should hold for writing.