I reckon it would be useful for the ship hull researches to just come with a simple +25XP or +40XP bonus to naval XP. It wouldn't help the AI per se, but it would at least give both the AI and player a chance to design a new ship around the new hull.
...or you could simply rethink, if you should need XP to add modules at all!
For me the actual use of XP (besides improving tanks and planes) is in general the wrong way!
XP should be used to create better variants of basic modules.
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