yep, modding SDK is scheduled for summer.
Oh god that reminds me, I was gonna have a little dig around the games files,
it actually has some modding capability already in the form of just editing some values in some Excel spread sheets
but there is not alot of sense in modding an Early Access game that gets patched on almost a daily basis.
honestly, I think if someone wanted to take Uboat and mod it to play exclusively like SH3, i think it will be absolutely possible with the finished product. Though If you get in to it properly, I'm not sure you want to do that.