Every centralized exchange and crypto currency has its own pathway on which it is running. I would recommend a making of a joint board of governance or a crypto Association run by just crypto community regarding the crypto assets. May be this time is too far but keeping in view many and many scams and lot of things it would do some things.
Do you think that this is possible to happen? if it is then there should be some organization that made this already.
1. There would be one main decentralized exchange for the crypto currencies to rule out all centralized exchanges.
This is a good idea, the volume of most will be there but this cuts the idea of being 'decentralized' because we're being pointed out to only one exchange.
2. Only authorized coins/tokens can be traded on that crypto exchange.
This is already implemented to every exchange. The coins that listed on them are being considered to be authorized on their part but this will be the start of the debate for every coin that has a supported community. But I go the idea of removing those scam and dead coins.
3. There would be one voice for crypto instead of too many voices where every just tells his own story.
But what if there will be other organizations that will build their own association too?