Funny you ask this, I've been toying with the idea of creating an attachment similar to the Benelli MR1 / Beretta CX4 Tri-Rail attachment. I have both, but I only tried CX4 attachment so far. It slides on easily and the concept is there, it's very obtainable to do with a 3d printer.
My vision is to add rails for grip and/or light, Tri-Rail attachment makes sense, while also keeping the aesthetics of OEM forend.
So after sliding the Tri-Rail on to get an idea, a few things I would need to do. 3D print Tri-Rail attachment that fits perfectly to OEM forend, making rails straight. Drill 4 holes on the OEM forend and somehow incorporate threads in said holes to screw the attachment in like the MR1/CX4.
Project for next year I suppose.