The most important job for witnesses is reliably producing blocks. Other jobs, yes, they can do too. When voting, different people consider different things.
Technically, the committee is able to decide the list of feed producers for each asset, that said, if witnesses can't do the job well, let others do it. The community can discuss whether this is a better way.
Another option, technically we can change the rules via BSIPs. For example, let bitCNY holders and bitCNY debt position owners vote for feed producers of bitCNY asset, vote for the related parameters, which could be fairer. However, this is tricky as well, for example, if a whale borrows a lot but doesn't sell, so holding some bitCNY in the meanwhile holding a position, perhaps it can manipulate the whole vote then can make a disaster. Perhaps let bitCNY holders/borrowers have some weight in voting but not 100%? Perhaps let CORE in collateral have zero weight?
Just brain storming. Please discuss.