Came to request this feature, and found this thread!
There’s something similar on the Koryuu, though I know its experimental, it’s the right idea of what I’d like to see. Definitely would love to see this feature with multiple steps of blur strength. I sometimes play with composite piped in through the Koryuu just to get this effect with the natural blurring of composite signals. I find composite + Koryuu + OSSC 5x with thin scanlines is pretty faithful to the original experience on a CRT. However, it would be better to recreate this with a cleaner signal of component/RGB.