In a way I could see a point to it. With unit sizes you'll have to carefully consider logistics of moving units over water, especially large armies over great distances. For example I build neanderthal elephant riders and they have huge sizes to begin with, but also very powerful when you merge them up, they can get very high strength and good for attacking cities. But to transport them on rafts I need to split up their initial normal size in to 3 smaller units for loading onto the rafts. With max 5 units of rafts transporting neanderthal elephant riders will take some real time. And I like this. It makes it MUCH more difficult to just show up with many sized up high strength units at enemies doorsteps. One sized up neanderthal elephant rider unit requires freighting 9 of the smaller downsized units on rafts, not something one simply do over night
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