What you are asking is basically whether the (theoretical or practical) knowledge of a system's transfer function can clearly determine its best controller.
The answer, like for most engineering-related questions is 'it depends'. As you are asking this question in an electrical engineering Q&A website, it depends mostly on what you consider as 'very good'.
Among all what could have an influence on the performance of your predetermined controller, we have:
- Uncertainties in system's dynamics
- Uncertainties in actuators' dynamics
- Disturbances in the system
- Lag and/or delays in sensors
How bad can any of the above be? How bad the effect would be on the system and how important is it?
If these uncertainties come with no real risk of either damage or performance, then go for your predetermined controller and just fine-tune it from there.
Otherwise the answer to your question passes through Robust Control: the science of making the best performing controller in a conservative world of uncertainties. Then, still, you'll be able to build a controller only given the same initial model, and some additional thinking and judgement of whatever could go wrong. It won't necessarily be 'good enough' but at least it won't break anything or kill anyone.