I just tried changing the "T" to a "10". I simply changed the T to a 10, made a new cards3.png, and sampled it on a few play money tables. The "0" in the "10" is almost completely hidden by the overlap of your other hole card. Obviously this wouldn't be an issue, for Hold Em, if everyone used "Full Card" option in the FT client, but I doubt everyone does. "Full Card" doesn't help the issue with the "10" getting overlapped, when playing O8 though.
For this layout, the "style" (font/placement) would have to be corrected based on the "10". The "10" if I use it, is the only card that requires 2 characters (2 unique characters). I built this deck, like all my decks, off the "A" card, as it is the most symmetrical character.
Sorry, but I don't see myself changing to a "10" anytime soon. I think the most important factor, for the upper-left characters is visibility. That is why I made the font as big as I could, to fit one character (a T not 10) on the corner, and be visible when the cards overlap in O8.