Great question, picking which data sources are safe to add will be interesting once the medianizer is built. For now, the goal is to develop a system that can take input from both offchain and onchain sources, and it will be up to the community to decide what sources are safe to add. Once we know how the medianizer is going to be structured, we can begin to discuss which sources the community wants to add in addition to Coinbase. I will likely start a separate forum thread once it is time to start that conversation. I will say I am partial to have many sources rather than just a handful, here is an interesting article to read related to the topic.