I'm largely in agreement with you, however:
How do you decide which universities are top 50?
What about specialist universities? I.e royal veterinary college or Harper Adams? Are they axed?
How do you make sure they are geographically spread? I.e a vast majority will be in/around London, how is that fair for people in Scotland, or Northern Ireland?
If they aren't geographically spread, and someone cannot afford living costs due to a small amount of student loan, how will they go to university, even if they achieve top grades? I think there are too many faults for it to ever be possible, although I do believe anything below 50 is pointless imo