well anyway those diodes are not that thick (1.5mm), at worse you may have to lift your switches a tinny bit off the board and most rgb ready switches have provision to place LEDs under them (where a 3mm led would go) although i do not have one on hand right now to measure if there is the 5mm needed. and if you have any good reasons to put them in the middle like that and that your calculations are good i do not see a reason why it should not work. if you have access to a 3d printer you could try to make a fake 4 switches (or more) pcb and try to make sure.