It would be pretty cool if, as high level league troops, the Japanese Navy's Yamato and the USS Iowa were available. Since there are no league ships currently, this would be a good way to add some. Iowa would have superior defensive capabilities, including HP, whereas Yamato would have very strong attack.
My other suggestion is, bring back the old ship firing animation, where they seem to use artillery instead of cannon fire. This is actually more true to life, and also just looks better.