Swapping position of Shimano shifter and brake lever
OK I understand. I have managed to swap the brake and shifter as you suggest, however, not his exact model and the components were worn - the gear shifter clamp had some play. If it fits, there is no reason not to. In the case I mentioned, I had to file down the cover of the indicator unit a little to accommodate the brake lever clamp. I also had to adjust the reach for the owner as the end of the brake lever was a little too far for safety. See page 64 for reach adjustment. https://si.shimano.com/pdfs/dm/DM-UABR001-03-ENG.pdf