Launcher = ESO launcher "outside" of the game where you start the game with?
This one:
It does not provide any scaling or size changing options or features afaik, so you either need to use any external software that is able to scale window sizes somehow (I do not know them but you should be able to search and fimd them with web searches like I did here:
https://www.raymond.cc/blog/how-to-r...or-dialog-box/ ) or you need to use the Windows build in magnifying tool.
About a new launcher: Forget it, it's against the TOS of the game and you'd get banned to change anything at the launcher and/or the game files, I bet.
You can start the game directly via eso64.exe file in your game's install folder:
DrviveLetter:\InstallFolderOfYourESOGameFiles_notTheFolderWhereTheAddonsAreLocated!\The Elder Scrolls Online\game\client\eso64.exe