I am currently using the "swap hands" functionality in QMK and set it to trigger at a long space press. When I press and release space, I get a space, but if I keep it pressed, the keyboard layout is reversed, so I can reach the buttons on the opposite half of the keyboard with the same hand. The nice thing with this setup, is that the brain easily can mirror the hand movements between left and right hand, so I use my index finger on the right hand to reach all letters that the index finger on the left hand would press. If you are able to use press some keys with the right hand, it can be used for occasional letters and modifiers, such as shift, ctrl, etc., that are a bit cramped to press with one hand this way.