Again, adding “for us” is a pretty big qualifier. So big, in fact, that adding it would completely nullify the meaning of “Alpha and Omega,” “First and Last,” etc.
Also, it should be noted that the first time the phrase “Alpha and Omega” appears in the Book of Revelation is in 1:8:
“‘I am the Alpha and Omega,’ says the Lord God, ‘The one who is and the one who is and who was and who is to come, the almighty.’”
In this first instance, as in the second, that phrase is clearly being used a name, a description of who the Lord God is. It is a global statement of His total being, not a narrow description of a single aspect of His ability. In order to claim otherwise, you have to pretend that “I am” actually doesn’t mean “I am.” And I’m sorry, but “they talked differently back then” is not a very convincing argument for why “I am” doesn’t really mean “I am.”
In short, when He says, “I am” He “probably means” “I am.”