I searched around for ages, looking for a way of making three macros that would let me reliably swap. Unfortunately it just doesn’t seem possible, as equipslot/pickupitem macros failed to distinguish between them.

However, there’s an easy way I’d overlooked at first – the ingame equipment manager. This seems to be able to tell the difference between identical weapons; you just need to create sets where you only have the dagger selected for change (so you don’t have to recreate the sets when you upgrade your head etc). Do this for each of the weapons, then you can drag/drop the equipment-set icon from the manager onto your toolbars. Easy!