I strongly disagree. Allowing such a thing would have precisely the opposite effect. Granted, disabled people might (and I stress the term) be able to find work more easily. But it would still allow discrimination in far too easily. If an employer knows that the law allows disabled people to work for less, they could very easily make a little pay cut that lowers the wages of disabled people in their company whilst still remaining within the law. It compels disabled people to accept the idea of being payed less and encourages discrimination.
Rather than tackling the issue in this way, Mr Davies should have made it his priority to tackle the attitude that would drive employers to hire a non-disabled person over a disabled. An employer that puts profits above people holds an utterly morally bankrupt position. The law should acknowledge this and counter it, not encourage it.