Changing / clarifying rules would I believe just be tinkering at the edge.
We already have rules which for the law abiding overwhelming majority of PPLs work fine. (aguments over free ferry flights etc excepted )
For what must be the very few PPLs who flout the law now, by doing blatant charter etc (according to other posts) then please explain what will stop them in the rule changes. The illegal brigade will already know that what they are doing is outside their flight privileges, so clarification won't make any difference.
I come back to something I said before..... If you know someone is acting illegally then you have a responsibility to take it to the authorities in writing. If they choose not to do anything or feel there is insufficient evidence, so be it.