Don’t think there is a way to scale that in any options. And you couldn’t do it with addons either since UI scaling and Addons are loaded after you log in.
Maybe if you do software scaling in like QEMU and run the output window fullscreen it might work, but I kinda doubt it.
OP is presumably talking about the list of characters on the right corner before you “Enter World”.
The three lines info including character’s name on the first line, -or more likely player’s nickname, since Speedstriker or Superbrutal for example is nickname, even though “Getoff Mylan” if we take the gnome mage few posts above for example can be considered as both name and pun on “get off my lawn”, I generally do not support naming character after players nickname, but that’s subject of different discussion- character’s level and class on the second line and character’s last known location on the third line indeed does take unnecessary lot of space and obviously, can’t modify that with AddOns.
If you have dozen of alts, all of them on single realm, it might be annoying to scroll through the list of characters. You however already have tools that allow you to sort the list to place the character that you play the most to be withing the top of the list.
I must agree though that it would be more tidy if the list display the full three lines only on selected character, and rest of the list will be displayed as one line containing only the name/nickname variation assigned to that character.
Unfortunately, Addons can’t access to anything before being logged in without breaking ToS. There as been some attempt to do personalized login and character select screen, but i would not recommend it.
Still, i do think Blizz should revisit it one day. I play on a a 32’’ monitor too and having the same amount of characters on the screen with larger buttons but not better textures than on a 12’’ feels a little cheap and blurry. They started to update it at the start of SL with some updates to the red buttons, then it was forgotten.
in the end, that not important, but it’s a nice polish.