what you have in mind to replace the extra flag? What I had in my mind to create the flag was this scenario:

get(key)// key is not local, it performs a remote get and it return null... now we have in context a MVCCEntry with key => null
in the same transaction, it performs an operation that must return the old value over that key (put, remove, get, etc...). What check can I do to say the null is the value and must not perform a remote get? Am I clear?

About the Read Committed, the method return always false.