I feel like its an exploit to surface your t1 subs on your naval factories early game as there's no way to counter it because when you push with any type of early navy all they do is hit the factories, not the subs so in theory 5 t1 subs with an acu and engis healing the factory could hold against 15 subs attacking.
I have no idea if this is meant to be a feature or if it's an exploit, I just thought I'd bring it to people's attention.
you mean putting your sub under your factory and then surfasing it? didin't know you can do that 
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I've played games where these kind of 'home-field' advantages work out to help balance by preventing pushes.
I can actually see how it might apply to Supreme commander, given that the 'anti-rush' measure is usually the commander, and the commander is limited in naval combat.
That being said, it's important to know that this exists, so I thankyou for the visibility, while being unable to comment on the balance implications. Thanks.