Some previous discussion about this issue:
-
[bitcoin-dev] CHECKSIGFROMSTACK/{Verify} BIP for Bitcoin (covered in Optech Newsletter #157)
-
[bitcoin-dev] Recursive covenant opposition, or the absence thereof, was Re: TXHASH + CHECKSIGFROMSTACKVERIFY in lieu of CTV and ANYPREVOUT (covered in Optech Newsletter #190 along with a list of other arguments against recursive covenants)