The most "helpful feature" you can implement for the OblivionLauncher.exe in 2021 (and beyond) isn't adding a new button, but rather
By 2021, many fans abandoned the official launcher in favor of Mod Organizers. oblivion launcher exe 2021
Even if you have DX12, you need the legacy DLLs. The most "helpful feature" you can implement for
If Oblivion Launcher.exe is gone:
TL;DR for real life: In 2021 (and still today), use OblivionLauncher.exe only to change graphics and enable mods. Then close it and launch the game via Oblivion.exe directly. For mods that need OBSE, use obse_loader.exe and never touch the original launcher for playing. Then close it and launch the game via Oblivion
The focus of modding The Elder Scrolls IV: Oblivion in 2021 was primarily on bypassing the aging launcher to ensure modern tools like the Oblivion Script Extender (OBSE) work correctly with the Steam version. Bypassing the Oblivion Launcher: A 2021 Guide