Anyway, I'm not sure why you think having some official rate would change much.
Let's say such a thing existed. How does that substantially help Bitcoin adoption?
For 4 year I was working as an exchanger and a merchant, selling goods for Bitcoin. I did all my best to spread adoption of Bitcoin at least in my country. Therefore I got certain thoughts which I try to explain.
Firstly understand why such systems like PayPal adopted easily. Let put aside that convenient fact that PP-USD is
almost equal to USD. "Almost" because due to fees on income and withdrawal PP-USD got less value than cash USD. Most important part that PayPal offers single point responsibility services to the merchant. Once POS plugged to merchant site it is PayPal who cares all from payment confirmation to exchange rate setting.
In Bitcoin especially in the first years from the merchant view what was offered was nightmare. Only geeks or total fans of Bitcoin would adopt it for business. Nowadays it looks much better while looking to POS system offers. But still they all have main problem which is looseness in exchange rate formation (which I explained in posts above). While in PayPal exchange rate is optional feature, in Bitcoin it is vital. Though situation improved but we have to admit that at the moment we can't offer merchant fully reliable POS solution. If it's self-contained box then it stores funds at a third party (which is anti-Bitcoin tendency). If it's privately held wallet then merchant gets whole load of headache to maintain POS system built on top of it.
Of course what I offer is not panacea which will make Bitcoin adopted everywhere immediately. I didn't promise that. It is just another step towards that direction.
And once more. Guys who sell things and exchange through forum (this one or others). No offense but it is not about you. I am talking about adoption by serial sellers. Small, medium, large.