They should pretty much just use the same fleet menues they use for EU4. Sometimes I feel like PDS has an aversion to use good solution from other PDS games
It has something akind to it when you select two fleets in that you can drag one ship class to the other and then you just have to click the list as often as you want to add e.g. a cruiser of that class to the other fleet.
I think they could expand that, the big issue is imho that pop up list of individual ships you have to scroll through.
If they used the above and instead you can say how many ships of that class you want to move and other quick filters like select all damaged ships they wouldn't even need to borrow from EU4 to get something decent.
Don't get me wrong, that ship selector list with auto closing tiny scrollbar is infuriating, but that way of shifting classes is imho a good start and actually more what one needs than that pop up ship list.
