Building bridges to other chains is the only way to avoid this from happening over and over again. Direct, easy to use bridges is the decentralized method.

This would flip the current model on its head as anyone could setup a bridge with enough tokens/funds to provide liquidity completely on blockchain.

You can see this being done by looking at what xBTS is doing here with BTS/Hive https://ex.xbts.io/market/XBTSX.HIVE_BTS

Centralized exchanges will be forced to become gateways, like xBTS above, instead of hosting their own trading environment. It's a win-win.