Because of the screen ratio, there's simply no space to do that on a Framework 13, without reducing key spacing: there is almost exactly 1 cm of space between the last keys and the actual edge of the frame.
On the Framework 16, I wouldn't be surprised if someone makes that: it looks like the design would accommodate a left/right-hand side narrow input module with the keyboard still centred.
On the Framework 16, I wouldn't be surprised if someone makes that: it looks like the design would accommodate a left/right-hand side narrow input module with the keyboard still centred.