Also, to build anything BIG, it’s hard cause you know we do eventually run out of certain blocks
Maybe that’s why he wants more Legos. 
Does anyone have another idea of the same theory as Legos? Something that just builds or continues with that type of mind set but isn’t legos and maybe pushes his ming farther.
If you go in a different direction then you’ll be adding something else that isn’t compatible and can’t be part of building something bigger.
Lego has a line of products called “Technic”. Instead of just blocks they get into different kinds of beams, rods, gears, and such. They are compatible with brick type legos but start pushing more into engineering concepts.
And we have Kenex’ but those just don’t do it for him?
I think they market K’nex to kids that are too young. Something about the building concepts they use doesn’t seem to spark an interest until kids get into the teen years.
The final level up in Lego is Mindstorms, which gets into robotics, motors, programming, and even more mechanical skills. I probably wouldn’t go in that direction yet because of his age. I don’t think he would fully embrace them yet if he’s not taking an interest in K’nex.