what i landed on is calldata suffix with tevm memory client tracing. will share code tomorrow (shoutout @fucory for building such an insanely powerful tool)

source for extracting calldata suffix from deeply nested calls

source for extracting calldata suffix from deeply nested calls
https://gist.github.com/stephancill/122401e327403281f42ebe842ef75f02

I know there are trace RPCs, but it isnt standardized, so they all differ slightly and are typically not available on free tiers. 

This method uses basic storage proofs that should be available in all RPC services