Welcome aboard CF 8)
Since you'll be building the stringer system from scratch I think putting the fuel tank under the sole makes sense. If I ever re-do mine, that's where I'll put it. The batteries could go in the console or if in the casting deck, that will free up a lot of room in the console. I don't know if putting tanks under the console makes sense though since they'll be a pain to get out. Look at
Mike's rebuild and you'll see where he put his tanks - great idea.
As for the boat sitting back too much with a 115 on it - I think it is ok the way mine sits with the 115 on it. It planes out nice and level with no tabs. The 115 is about 320 lbs - I wouldn't go with anything heavier.