Wheel Adapter / Spacer

How would I make a mod that acts like a wheel adapter/spacer? I would like to be able to attach it as wheel and then attach a wheel on the other side of it. it would have adjustable wheel spacing (with a tuning slider) and can convert say a 4 lug hub to a 5 lug. I want to make it as a proof of concept for now. If it works, I want to know how to model it to stretch the adapter model with the spacing the user sets.

 

Just an idea but maybe you could just extend the bottom suspension arm, this may have unwanted effects but may be easier than making a spacer, that to my knowledge nobody has done before.
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Or maybe even just come up with a new set of wheels, considering that the stance communtity that use spacers do not usually use the wheels that are available in beam, they look more aftermarket and have a super deep dish to bring the wheels out further.

 

I still want to be able to have a mod for adapting hub type (4-lug, 5-lug, 6-lug, etc) and add extra spacing to the wheels without modifying each individual cars supension