Great idea! Actually the mk3 of the PCB had these parts on the bottom. The reason for putting them on the top layer was that this way we can decrease the thickness of the macropad (we don't need much space between the pcb and the backplate). For now it is basically a tradeoff. One way of improvement could be, that we don't use a BLE module, but solder the MCU directly to the PCB and use smaller passive components. This way the max. height of the components could be decreased and we could put them back on the bottom. This would also mean I have to design the RF parts, which is very far outside of my knowledge.