FUSE being a fundamentally scarce resource, should be quite ideal to use as collateral. So if, there ever appears lending protocols on the Fusion blockchain, I can see this as quite a natural usecase for FUSE. Perhaps also for FSN/FUSE, but it would be less ideal, in my opinion, as the collateralized FSN/FUSE couldn't  then be used to vote. Sharing some TL  FSN/FUSE on the other hand makes perfect sense, since it has an active time value flow and could likely still be used to vote as long as you still hold the infinity end of it.