That is exactly what weidex has. AS far as I know they do have their own coin WDX which is same tokon for its transaction fee on the exchange. But I'm not sure if it will really attract traders to stick in the weidex exchange. Increasing liquidity is always an obstruction to the progress of every DEX. Bitshares is one of the oldest DEX I've used but its not as friendly as it looks and up to these days its volume still is less than a Million USD.
Loads of decentralized exchanges built on Bitshares platform, but most of them have nearly same core issues. They are not issues of only Bitshares-based decentralized exchanges, but also are common issues of DEXes. I can not imagine how DEXes will change their approaches to provide support for their users when private key backups lost. I guess it is possible, because if there are support teams, whom are responsible to solve issues with sticker orders; they should be able to solve tickets on private key lost. It is likely related to technical limitations of DEXes, at the moment.