I think Personalised Number Plates could be a force for good. The DVLA should stop selling them though. They should rent them out. They should remove the restrictions and just allow people to have any word they choose. Every few years the plates should be re-auctioned. The current holder can choose to match the winning bid if they want to keep the plates.
Maximise the income from them, and make it recurring.
Ultimately if some meff wants to pay lots of money to the government coffers, it is a good thing, and they should be milked for as much as possible. It is an ideal "tax". Something completely non-essential that someone chooses to have.