I don't think the idea is silly. The thing is, you are suggesting people to store 2 seeds instead of one with this failover address.
If people lack responsibility to store one seed, they will just store 2 seeds together.
You can split your seed, use a mnemonic phrase, etc to increase security.
Like I explain in my last answer, it is pretty different from using a multisig wallet since one key is enought for most use, the second one will be only for emergency cases. For example the main one could be even use with hot wallet and the second one stored in much safer place or even escrow service.
I dont see how this is different from a CLTV setup tbh.
I am not, an expert, could you explain me what a CLTV setup is please?