-four-wheel steering with Hand of God and working cockpit steering-wheel
-pendular front axle
The model is not based on a particular machine and it's made in the style that's more common in the USA than is Europe: the backhoe boom is centered and fixed (no sideways movement), but the stabilizers have wider base.
The pneumatic switches are placed on the sides of the model. They are easy to reach and to operate carefully, but hidden enough not to be visually distracting. There are two separate circuits on each sides, so two functions can be operated at a time with two hands without the functions affecting each other.
The functions are grouped together in a convenient way for a right-handed person. Backhoe: left hand for swinging and dipper elevation, and right hand for boom elevation and bucket curl. Loader: left hand for boom elevation and right hand for bucket operation.
The model is big enough to hide the tubes so the cockpit is not crammed with tubes.
Pneumatic power source:
A Power Functions medium motor driving two pumps for the two circuits. I decided to use a compressor instead of a manual pump for one main reason: Operation is much more convenient with two hands. But two hand operation requires two separate circuits because operating two cylinders with one circuit means that the cylinder with the higher load won't move until the cylinder with the smaller load moves to its extreme position. This means two manual pumps, which is not cheap/easy to get, and it's hard to find a place for them where they aren't visually distracting.
Front axle and steering:
The first axle is pendular: not a rigid axle as in real life, but an independent suspension with the two arms connected with a beam. The wheels stay more vertical and more away from other parts which is important as the things between the wheels are already as narrow as possible (the front loader arms, body panels and battery box are all there). Another advantage to a rigid axle is the stronger chassis and wheels support (the vertical space for reinforcing the chassis and supporting the axle from both sides is limited by the battery box).
The wheels still touch parts when fully steered but there's no jamming or noticeable resistance: the front wheels can touch the arm elevator cylinders and the rear wheels can touch 1-1 rollers placed there deliberately to prevent the wheel from jamming into beams there (the extra rollers wouldn't be needed if the hub parts didn't have so much backslash).