If I wanted a mechanical keyboard, I'd buy a mechanical keyboard.

If I wanted an electronics project, then I'd repair it.

Not to diss electronics projects. I've done those myself, and they can be rewarding. But there's a reason that repair shops aren't much of a thing any more. Just usually doesn't make sense economically.

If you very specifically want an exact keyboard that's out-of-production and where the only way to get one is to repair, or you very specifically want some particular feel that isn't available commercially, then maybe it's worth putting time into it, aside from the project value.