I'm sure it's possible but you would more than likely lose some effectiveness. The people who make these wheel cleaners spend a lot of time formulating them to work as planned without any negative side effects. The emulsion systems and concentrations of different solutes are designed to be effective with eachother, and by adding anything else to the solution there is a chance of interaction between chemicals that could be caustic, poisonous, volatile, and possible explosive.
For instance if you are using a wheel cleaner formulated with hydrofluoric acid and various surfactants, then go and add something with ammonia in it; you will have a major incompatibility leading to the evolution of hydrogen gas which ignites at the slightest hint of heat.
