Regarding liens, it seems simple enough to say that if someone does not own an NFT "free and clear", then they cannot transfer it "free and clear". It might even be a different NFT entirely (a "liened NFT," where the original un-liened NFT is held in trust by yet another smart contract, with limited or conditional ownership rights given to the lien holder.)
The reason not to use a database is interoperability. Any smart contract can transfer these NFTs according to infinitely nuanced scenarios, and only during disputes would a court need to get involved and forcibly transfer the NFT according to a judgement.
The typical case where all is not equal in finance is where currently parties transact via a trusted intermediary like a clearinghouse (who might take a 1% fee, say), and a startup wants to allow parties to transact directly, thereby capturing the fee as upside. Large financial institutions don’t tend to trust small startups that might implode any month, but they can (sometimes, it seems) be persuaded to trust a distributed ledger.
Before I buy an NFT, I'll have to check the GovLedger anyway to make sure that NFT is actually that person's to sell, and hasn't got a lien on it or something else that means they can't actually sell it.
If the idea is the blockchain is permissioned and the state can choose which transfers to allow and can forcibly recover NFTs, why not just use a database?