The only way I see that submarines could be added and everyone will be happy is that submarines have their own game-mode where it is different maps for different tiers. Each tier has 3 maps that get randomly chosen. for example. t1 has 1 map that only allows for t1 submarines. t2 has 2 maps only for t2 subs. t3 has 3 maps limited to the tier 3 only. t4 t5 t6 t7 has 4 map choices but they are limited to only fight the same tier. Like in ranked. t8 t9 t10 has 5 maps that are specially made to fit the size of the bigger subs and are deeper. the skill-tree is special for submarines only cant be used on any other ship except submarines. free XP cant be used on submarines. or commander elite XP on sub captains. to make it fair. special XP and free XP called sub free XP and sub commander XP. for submarines. destroyers have a new consumable called depth charge when it is mounted the destroyer you mount it on will get locket into the new sub-mode. untill that consumable or mount is unmounted. Radiolocation skill does not work against or on subs. camos don't exist for subs. flags do not work for subs because they are underwater.