well I disected it to investigate, and yeah you could put an external antennae on it, it simply has 2 wires soldered onto the pcb connecting its own mini external one, and no damage would be required to install an external, as the mini one leaves a hole of about 8mm for your new cable,
Come on, you know you NEED it, without this mn500 your life just wouldnt be complete, and what a bargain at 175quid cor blimey mate ya cant go wrong, lol