The Giants recruited Addison as a delisted free agent on Thursday after the Western Bulldogs showed him the door last week while the Magpies did the same with Armstrong following his axing from Sydney.
Nahas hasn't officially joined the Kangaroos but the club has signalled its intentions to recruit the former Richmond small forward as a delisted free agent on Friday.
Addison was given his marching orders by the Doggies after eight years at Whitten Oval which saw him play 88 matches and kick 30 goals.
The 26-year-old, who played predominately as a defensive forward in the past two seasons, announced his intentions of continuing his AFL career elsewhere following his delisting by the Dogs and the Giants have answered the call.
Collingwood have taken a punt on Armstrong after a barren six years which has only yielded the 24-year-old 29 games in total at Adelaide, where he spent four seasons, and Sydney.
Armstrong, who debuted with Adelaide in 2010, was drafted by the Crows with the 58th pick in the 2007 draft before being delisted at the end of 2011 and subsequently recruited by Sydney where he has spent the past two seasons.
Meanwhile, Kangaroos list manager Cameron Joyce confirmed Nahas was poised to add to the 83 games he earned at Richmond by arriving at Arden Street on Friday.
"We feel there's a very specific role for someone of Robin's talent and he'll be a great addition to the club," Joyce said of the small forward.
"He'll bring some more speed to our forward line and just as important, some more defensive pressure in our forward half complementing the likes of Lindsay Thomas."
Elsewhere, Carlton have continued their Irish experiment by signing Gaelic footballer Ciaran Sheehan as an international rookie for 2014.
Sheehan joins established defender Zac Tuohy and new recruit Ciaran Byrne as other players from the Emerald Isle currently on the Blues' list.
Carlton have also had Setanta O'hAilpin and Aisake O'hAilpin at Visy Park in recent years.