I have a suggestion about items. I think, there should be some items about expedition. This items can be appliable for each wave of expo fleet seperately or whole expo fleet. Prices for these two situation can be different. Here are the two suggestion of my items:
1) No delay: When player used this item, expo fleet won't come back late.
2) No destruction: When player used this item, there's no risk of losing fleet.
There can be several other items but i just want to give some example. I know, when this items put into game, there is a risk of being expo class superior than others (in my opinion, it became already). However, these items can be worth to spend DMs. Also, it can provide more comfortable game playing to some players. The main point over here is prices of these items. With appropriate prices, doubts about them will be removed i think.