This sentence seems like an oxymoron to me:

>> True meritocracy can only come through promoting diversity.

If you are taking diversity into account, you are taking things other than merit into account and so it isn't a 'true' meritocracy. Not only that but it also suffers from the no true Scotsman fallacy.

The best way to promote meritocracy is to base your decisions on merit and nothing else. To avoid unconscious bias, you would have to hire someone without knowing their age, sex, sexual orientation or anything else that you could consider discriminatory. That would mean hiring someone that you haven't and that's a little extreme.