At a conceptual level, there are four possible outcomes of VSU payment:
- a person will pay, no matter what
- a person would pay, but can't be bothered
- a person would pay, but can't afford it
- a person won't pay
Like I've suggested, instead of satisfying certain groups, why not seek a common ground? A system where you could choose to contribute, but where the government / university provides a 'lubricant' of sorts. When you reduce the opportunity costs by simply providing a check-box: 'do you wish to pay your union membership through your HELP loan', you satisfy the middle two groups. The fact you can pay at all will satisfy the first and that you can choose not to pay will satisfy the last.
Ideology is can be a good way to guide decision making at a high level, but when it really counts, you really do have to be pragmatic about it. And, in reality, each sector is going to have its quirks that will cause policies by a person spitting out ideology fail at least some of the time.