i don't think the idea of doing some sort of test or course is a bad idea, many immigrants who have lived here for years and have made the uk thier home, but they cannot read, write or speak english.
if the person already has a understanding of english, then the life in the uk test can be taken to prove it, and as they need to be tested on some subject, why not the uk ?
for those who think they cannot pass the test, they can do an English course combining the citizenship info.
it's a waste of time for brits who speak english and maybe for those immigrants who can take the test straight away, but i'm sure it's not for those who are on the English and citizenship course, by the time they finish the course they will have a better understanding of english