I suspect that as some have already mentioned, it will become a tax, either on earnings or most likely added to council tax. This will be good news for those who don't work or pay any tax as those who work will be paying it for them.
I suspect that this is the real reason why Labour are in agreement with it becoming a non criminal offence, it fits in with their political policy where those who work to pay and those who won't work get it for free.
Such a method of collecting the licence payment would be unfair because it would be compulsory for those tax payers who do not view the services.
Subscription/conditional access is the only fair method