My one concern explot wise is, a situation where a naval and land power ally publically or secretly. When the land power state wants to engage in a colonial war it "buys" 200 ships at an enormous discount from it's friend, then fights and wins its war returning many of the ships back to the naval state. Later the naval state wishes to engage in a war in which a large land campaign needs waging. It buys 250k men from the land state at an absurdly discounted price and wins its war etc. etc.
The issue I see with this is that it's not only ahistorical (in the amounts of exchange people will be doing, not small scale mercenaries) but well as you all can see it can totally throw sky high any idea of equality between nations or naval/land advantage. BB could contract england to build 300 warships for it not only at a cheaper price then BB could but at a secretly reduced price on top of that ... allowing BB to effectivily fight a large established naval power with ease and without official allies.
Hehe, naturally I used tem's nation for this example

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Parts of this I like, others ... i'm more cautious about.