Mercury got listed on Bittrex in last months as Waves token. So it doesn't seem impossible.
There are far less Waves platform tokens on centralized exchanges than Ethereum platform tokens but like you said, it's not impossible. Tokes (TKS) is also a Waves platform token that was listed on Bittrex for a while now. There will be more Waves platform tokens listed on Bittrex and similar exchanges.
If that's the case why Starta is still not on Bittrex or Polo or Binance? What is stopping them from making it to these exchanges? any word from the team on any hurdles ?
I don't think it is that easy to be listed on those ones. And they're doing buyback, it is also affection the listing because of regulations.