The smart contract you build specifically needs the collateral token/coin to be on the same chain or network. That won't work for some lenders or borrowers. If I want to lend a bitcoin, how do you(the smart contract) make sure it stayed as it is, without wrapping it to another token, say, WBTC? it applies to another altcoin, Monero or anything that isn't tied to what the smart contract platform is built on.

Last but not least, as you stated by yourself that it is just the same as other lending platforms within defi, what makes your platform better than the others?