Here is my suggestion for a fair system of cover exchange:
Allow us to gift/trade the first cover of each power between alliance mates.
Example: Say i have a Patch at 0/5/5 and a spare 
Rocket&Groot. An alliance member has a spare 
Patch and his Grocket is at 0/5/5. Since both heroes are off rotation and the DDQ for their first power has already run, we will have to wait until they get back on packs for a chance at getting. Now here comes the solution: Those two player could swap their covers and from there use their hp to buy the remaing covers.
Another example: I have an extra mystique cover from the last event and an alliance mate does not have any covers for Mystique, because he couldn´t play the last pve and the alliance was not a top100. His pve score will be seriously hurt since he can’t play the essentials until he gets her through progression. Allowing me to gift him my extra copy will let him stay competitive on the event.
The beautifull part is that it can’t be exploited. Now you may say:
It will allow the top alliances to monopolize PVP even more
It will not, by simply having the cover immediately used upon pick-up. Even if 5 members of your alliance scored 3 covers each on a PVP and gifted you them all, simply picking one would lock the remaining ones of that color and send them back to the original donors, preventing a exploit
It will make newbies on good alliances curbstomp other newbies with them
It will not, because unless said person spends a massive amount of 
& 
, a 
character with one of each cover has no chance against a much easier to cover maxed
It will devalue
and let people exploit DDQ since everyone will have a copy of them
It will not, as player would be limited by their roster slots. If someone started playing today and received one cover for each character, the only way to have a roster with enough space would be to spend a massive amount o HP. Also they would need to have
to stay competitive or drag themselves with
1/1/1, which would require a even bigger number of roster slots.
This a change that would favor mostly
to
transiotioners, without hurting the other tiers of players.
Why would it be good?
-People will have better acess to DDQ Daily allowing them to fasten they transition
-PVP will turn out more competitive as more players would have acess to featureds with key powers instead of just a loaner
-Can be seen as a player investment: Gifting a player a cover so he can perform better on a event can push the alliance from 51th to 49th, therefore being benefitial for both parties. Also, it`s sad to sell a
for 500 iso and see that warning pop up
Also since you only need one cover on a power to buy its remaining levels, it would turn out as profit for D3 (Capitalism, Ho).