The hardest thing when creating a radio controlled tractor or construction vehicle is fitting all the components into the model, accessories can help with this problem. When you are building your RC tractor you might want to use a small battery that wont last very long when the tractor is moving on its own and then have larger batteries hidden in a trailer which can be easily connected to the tractor without looking out of place. Alternatively, if you have a very small vehicle, you might choose to have the batteries permanently hidden in the accessories with no batteries in the tractor.
Trailers are a great place to hide batteries because their size usually means they can serve other functions, for example if you have a dump trailer you are going to want to be able to dump loads of sand or gravel. If you have a steerable mower conditioner you are going to want to be able to steer it through some tight gates into fields to really test out your driving skills. My point is that building these radio controlled machines is only half the fun, you want the to have functions so that you can enjoy using them. Something as simple as a bale fork on the rear lifting arms can make your RC tractor infinitely more fun because picking up and delivering the bales is more challenging that just driving around.
This section lists the various trailers and implements I have built for my RC tractors. If you want to control one of these from a Siku Control 32 model I suggest you add an NRF24L01 radio module to the trailer or implement and control it using the Basic RC Controller.