I would, for weekly missions, cut in two parts.
One part with a 5 Missions Chain
A second part with a single mission with two requirements being
First : Complete the mission chain
Second : Specific Type/Nation skill requiring mission.
So, Chain mission (Tier IV to X):
First : Kill 5 Ships (In any number of battles) Reward : Credit Container*2
Second : Deal 50000 Damage (In any number of battles) Reward : Consumable container*2
Third : Be the first to spot 2 ships & Get 20000 spotting damage (In any number of battles) Reward :Flag Container*2
Fourth : Hit 100 Main Battery shells & 15 Torpedoes Aerial or Ship (In any number of battles) Reward : One of each container
Last : In a single battle earn an heroic achievement and join the top 6 of your team. Reward : 5 Random containers and a "special upgrade"
The parrarel "hard" mission (T VIII to X) :
- Finish all 5 stage of the chain
- In a single battle Win with a Britsh Light Cruiser, dealing over 125k damage and being first of your team.
Reward : 24h Premium, 10 Containers (From which you can chose the type, thus having a SuperContainer chance), A special upgrade (different from the chain).
The idea with this, is to have a chain that everybody will be able finish, easy to get with not so bad rewards but not great either, that's a total of 14 Containers and a "special upgrade".
In parrarel a much more difficult mission, requiring the player to have the necessary ship type but giving much more important reward. This would allow everybody to get most of the rewards, players able to only do the chain would not feel spoiled by not being able to do that extra hard mission because it is tagged has a hard mission made for long time players with lots of ships and because the rewards are close to what they got already in the chain.
At the same time the long time player with all ship line grinded can get a weekly 24h premium and goodies to reward him for being a long time player with many ships in his port. Of couse rewards can be tweaked and changed weekly, I used containers cause I feel it's a good way to balance things without giving it too much thoughts, but the most important is the idea of it, having an easy chain for everyone and a parrarel hard mission for the hardcore players.