hOHMwardbound new loan origination could be prevented on the DAI set by removing the treasury permission to access DAI; then a new clearinghouse could be set up lending ETH. I would see that as the way to transition from one to the other. Rollover would persist though, yes. I don't think having both concurrently would work well but to be honest, it is hard to conceptualise and I've mostly put it aside.
Joel33 the proposal does prioritise holders over the protocol itself, but it does so knowing that it benefits all holders equally. I see this as the same dynamic in which staking emissions benefit holders more than the protocol. That is why targeting some fed-funds related rate does not make sense to me. Regarding the difference between Vendor and Cooler, I see it as having a strict loan-to-collateral versus a loan-to-value. Vendor uses an oracle to determine price, then lends a percentage of that price. Cooler lends an amount per collateral token. Vendor might be better for other tokens but in this case, with the concept of backing, I see Cooler as superior. There is also the matter of needless expense on fees, which you point out.