Guidelines would indeed be necessary for the people who would be reviewing applications, in order to give them parameters and prevent any arbitrary application of this provision.
We need to ask whether compassionate grounds might include instances in which certain people need flexibility because of financial limitations or other factors. Health problems could also be considered on compassionate grounds. For example, could people who have cancer have an exemption, while others with different health problems would not? Determining who is entitled to flexibility and an exemption is a difficult process, and we would like to avoid requiring officials to rule on these. The application of this provision needs to be more consistent if people are to have ready access to the flexibility they need, for all kinds of reasons. It should include financial or other considerations in addition to health constraints.
That's precisely why the regulatory proposal was put forward: to give applicants the opportunity to take part in their citizenship ceremony in accordance with current procedures, or to do so online at a later date.