This is a really good and important question raised by @mattimost.
Comet was designed with simplicity in mind, so there are only two speeds: one for supplying and one for borrowing. This approach is effective for systems utilizing a single incentive token, such as COMP. However, it falls short in systems with multiple incentive tokens, since each incentive token would need its own speed.
On the technical side, there are a few different ways to support multiple incentive tokens. The approaches are listed below, but would require upgrades to Comet and introduce more complexity and gassiness to the protocol:
- Store a list of speeds to support an unlimited amount of incentive tokens.
- Move management of speeds and incentive tracking to the rewards contract. This would require Comet to call into the rewards contract using a hook on every state-changing interaction (e.g. supply, withdraw, transfer) to update the tracking variables.
Given the uncertainty around the length and scale of Coinbase’s marketing campaign, the community might need to eventually switch over the COMP incentives regardless. Taking this into consideration, sticking with the status quo of only distributing COMP in this new market might be the more straightforward and practical approach.