How much of a retcon is the Ambassador choice going to have?

Since its temporary it will not have any consequences. I still feel Raeka is the right choice, might as well get the pathfinders into the leadership since they have to solve everything anyways. Finally nexus's main problems lie in not having clear leadership.

They did not tack it on only as a plot device, it was on purpose to prey on people's sense of nostalgia. This is what I don't get: OT was littered with inconsequential decisions and they chose not to learn from that. Udina or Anderson as ambassador? Doesn't matter. Destroy or keep the greybox? Doesn't matter. Thats OK, hindsight is 20/20 and at the time maybe thought those choices would be cool to have. But its been 5 years since the OT, and they still can't help themselves, they introduced an ambassador choice. He is an ambassador to the Nexus to represent the Nexus (whatever that means, horrible writing and only reinforces that its a plot device).

So why include it? For the same reason there is a giant remnant worm on Elaadan, some dialog about Okeer, an old Krogan trying to improve the lot of his people, a turian with the name Kandros, and finally the same reason Alec Ryder's big secret is the reaper invasion of the MW. They wanted to cash in on the nostalgia people had of the OT.