Combined CTV/APO into minimal TXHASH+CSFS

The discussion revolves around the complexities and considerations involved in introducing upgrade hooks to a system, with a specific focus on their application within the context of coding practices. The debate highlights the inherent challenges associated with adding upgrade hooks, suggesting that opting for an alternative opcode might be a more straightforward solution. This perspective is particularly relevant when considering the limited availability of upgradeable NOPs (No Operation codes) within the system.

A significant point of reference in this discussion is the decision to omit CHECKSIGFROMSTACKVERIFY from the CSFS (CHECKSIGFROMSTACKVERIFY) BIP (Bitcoin Improvement Proposal). This decision underscores the careful consideration that must be given to the implications of incorporating such features. It illustrates a scenario where, despite the potential benefits of an upgrade hook, the broader impact and limitations led to a conservative approach.

In essence, the conversation underscores the need for a balanced and thoughtful approach to the evolution of coding practices, especially in environments where resources or options like upgradeable NOPs are limited. The example of CHECKSIGFROMSTACKVERIFY being dropped from its BIP serves as a cautionary tale, reminding stakeholders of the importance of evaluating the long-term ramifications of such decisions.