Obviously its no trivial matter you shouldnt add a fourth spec for the sake of having it. But when you need to dynamically change a spec that replaces more than half its mechanic, it is worth considering that may need to be an option. Especially when this change happens in the middle of an expansion, you have a shorter test and balance phase to get it right before the deadline to release.
Keep Marksmanship as it is, create a new spec with the petless, Eagle mechanic. You put a lot of thought and effort making this new design, it would be heart breaking to see it end up scrapped. A fourth spec to introduce this complete overhaul playstyle may need to happen.
Also let the community choose the name, maybe? You select the names and put it to a poll. Obviously dont let us pick an option else the spec would end up named “GarroshDidNothingWrong” or “ShootyMcGee”
Alternatively, bring in an arcane archer type 4th spec (black arrow, explosive trap, arcane shot, serpent sting, wind arrows, wailing arrow) for those who want the fantasy of a natural magic hunter and pet. Basically a mix of old Survival and Legion MM.
Then, allow Marksmanship to be just about physical damage arrows.
That’s IMO the flavor that’s gotten lost since the Survival melee change.