The writer, Moonsettler, expresses a belief that signature aggregation will become the primary method of using CSFS (CHECKSIGFROMSTACK). Specifically, they highlight that LNhance, which integrates both CTV (CheckTemplateVerify) and CSFS, would benefit from having these functionalities available before the adoption of tapscript. This indicates an understanding of the importance of these features in enhancing Bitcoin's scripting capabilities.

Moonsettler remains neutral regarding the proposal for CHECKSIGFROMSTACKADD but points out some concerns about backporting Schnorr signatures in this manner. They note the awkwardness of the NOP upgrade path, which leaves three elements on the stack as a downside. Additionally, there's an acknowledgment of the complications that might arise from reverting CSFSV (CHECKSIGFROMSTACKVERIFY) to use ECDSA in pre-tapscript environments. This could necessitate the consideration of implementing script-based multisignature solutions to achieve meaningful security improvements.

Overall, the email underscores a thoughtful examination of the technical pathways for integrating advanced signature and verification methods into Bitcoin's infrastructure. It suggests a cautious yet innovative approach to evolving Bitcoin's scripting and verification mechanisms, with a clear inclination towards making foundational technologies like CTV and CSFS accessible ahead of broader script updates.