Ds8 has been like that from about 3, a lot of times he has these grand designs that there is no way he is going to be able to execute on his own so we work on things together. Mostly take-offs on things he has seen. I knew things were getting a little out of control when he asked about building a large ship in the front yard. It took about 1/2 a day of debate and then I finally just sat down and started working out the cost with him, showing him the formula for the area for each side of the proposed ship, deck, etc.
Not to be discouraging, but, really, I just couldn't build a ship with him! (Not this year anyway)
He is constantly working on new drawings for robots, armed people/things/ghosts/etc., cars, flying things, etc. etc. Other times he will build models of things he wants to build larger with cardboard, tape, odds and ends. Yes we have trouble getting cardboard boxes out of the house too!
I am vaguely considering getting some welding gear in a couple of years...