6 months ago Brannon said on twitter that that had been the plan since day one.
Most people think he's lying. Maybe it was a half assed inkling in competition with other half assed inklings, but there's no way it was set in stone as the big reveal primed for a delayed gratification 3 or 4 years down the line.
In 2001 when Enterprise started, anyone who made a list of who Future guy might have been, they would have put Archer on that list, and then crossed it off because it's way too cheesy, only slightly less cheesy than making it John's dad Hank.
Or is that not what you meant MacLeod?