Many players have  medals of other races. Some of them are usefull, others are not.
I propose to introduce exchange between alt accounts.

some limitations:
-only fleet  and received from expediotion medals are interchangeable
-exchange is not to make too often

The beastiary covers this. Yu cant' trade achievements but you can unlock the achievement get the corresponding fleet and sell it in the beastiary.

you can also unlock the achievement, get the corresponding fleet and destroy it by sending to the stronger player - it's pointless but you can. Or simply forget about the medal. So by writing "the beastiary covers it" you exaggerate a little.