Emulators of the most popular consoles can run many games in widescreen today, is it possible to add support for this?

• Genesis: Genesis-Plus-GX-Wide is widescreen core.
• SNES: bsnes has a HD mode that supports widescreen.
• N64: Mupen64Plus-Next has a widescreen hack. Maybe also possible with other cores. Here is a working web example by NeptunJS, I assume they used Mupen64Plus-Next but not sure.
• PSX : both Beetle PSX HW and SwanStation have widescreen hacks.