Eitech makes a range of sets to accommodate different skill levels. The largest of their sets can have up to a 1,000 pieces. Shown here is their massive Deluxe Motorized Crane Construction Set.
The also sell an assortment of different accessory packs featuring spare parts, motors, gears, and solar panels. These could be useful in their own right for making prototypes or gizmos of your own. And...if you are into construction toys, this looks like quality stuff.
Here a link to the dedicated Eitech store.