For GPBIKES, you need add a turning angle on the handlebar
ar.
For Gpbikes and good older simulator games :
Your springs at the base are a good idea but it would distort the conditions on the road . i'm make 110 kg, so, sure you can sell tha's for a little boy with my pound???
After that it can be added as an option, but for the precision it is necessary. perhaps 4 shock absorbers with potentiometer to control the central and lateral, center and front rear places in the four coin.
Unless it's just for arcade games for others basic games... no necessary a home simulator....you can play to motogp17 with a simple joystick vibrate is the same sentation.....