How about restricting city status to a top twenty/ fifty settlements? That way it would have to mean something.
As things are going, gaining city status is going to be a box ticking exercise rather than joining the elite. You know the way that climbing Mount Kilimanjaro used to be a significant achievement, then it became the benchmark for thousands of people doing charity fundraisers and lost the "cache" that it had? Or getting straight "A"s at GCSE/ A Level was quite something, but then became "the norm" so that they had to increase "A*" etc.
As a suggestion:
* - Places with a population of over 250,000
* - Places with three/four digit telephone codes (e.g. 020 for London, 029 for Cardiff 0141 for Glasgow, 0113 for Leeds)
* - Places with single letter post codes (e.g. B for Birmingham, S for Sheffield)
Population of over
Forget cathedrals (so few people attend regular church services), forget things like Mayors, make being a city something meaningful or forget about it