Unlike the other two challengers, Steve Turner and Sharon Graham, he is not currently a serving officer with the union. Neither is he from Labour's hard left.
It's the perfect fit for Mr Coyne, from West Bromwich, whose whole campaign is about offering something different to members he believes have been let down by a union that has been lead down the wrong path for years.
He says he's the man to put things right, with an agenda for "real change" that will focus on benefitting members and cast off all the Westminster baggage that has weighed Unite down.
After being narrowly defeated by Len McCluskey in the election for general secretary in 2017, he is hoping to go one better this year.
"When I stood in 2017 it was very much about how the union had got to change or face terminal decline, and that message hasn't changed," he tells me during a break from a picket line he had joined with workers at GKN Wheels and Structures in Telford.
"The other two candidates were part of Len McCluskey's campaign team back then and here they are now actively supporting a continuation of more of the same.
"I'm saying we need something different, and that starts with a change agenda that focuses on the world of work as it is now in the 21st century, not as it was.
"It's time to open up the shutters and let in light to the organisation."
The 2017 campaign was a bitter one, ending with Mr Coyne getting sacked as the union's West Midlands regional secretary over an alleged data breach, which to this day he claims was a "stitch up".
This year has also seen sparky fly, with leftwinger Howard Beckett pulling out of the race last month and endorsing Mr Turner – who has subsequently been backed by Mr McCluskey – amid claims by Mr Coyne that a "grubby backroom deal" was being struck to try to stop him from winning.
"It tells you all you need to know about about how frightened they are about me actually being successful," Mr Coyne says.
As part of his agenda Mr Coyne, who joined Unite 35 years ago, has committed to giving more support to members and workplace reps by investing in technology so the union "is at people's fingertips".
He plans to launch a £10 million skills fund to boost training opportunities for members, and wants to create a Unite 'kite mark' to recognise quality.
Mr Coyne is also determined to bring in new measures to improve financial accountability and transparency, and has pledged an independent investigation into Unite's Birmingham hotel and conference centre, which has seen costs spiral towards £100 million.
"That's nearly £100 for every Unite member on a four-star, luxury hotel and conference centre that sadly many of our members will never have the opportunity to experience," he says. "It's completely unacceptable."
He says a huge drop off in membership over the last four years proves that something needs to give.
"When I speak to members I can almost touch the desire for change," Mr Coyne says.
"I don't know whether its because they want a new start after the end of one general secretary's tenure, or because of the pandemic, which lots of members have worked through.
"A lot of them have told me they struggled to get in contact with their union. People want a different organisation, one that's more responsive, that's quicker and is there when they need it."
He says it is a "real problem" that the union has become distracted by events in Westminster and must end its focus on being the "backseat driver" of the Labour Party.
"It has not been beneficial to either organisation," said Mr Coyne.
"I want us to be a strong voice for the world of work, and if we are growing rather that losing members year on year, then across the political spectrum they will have to respect what we say.
"Unfortunately too much time has been spent on believing a Labour government will come over the hill to be the saviour of Unite. It hasn't materialised and its not likely to when you look at how high the bar is to win back a Labour government.
"We've got to absolutely focus on the day job – and it's a big enough job without messing around with Westminster politics.
"That's not to say that politics isn't a component. I want to see a Labour government, but the pendulum has swung too far in one direction away from a more mainstream approach on jobs, pay and conditions, which is what members pay their subs for."
With ballots now open for the election, which will see a winner declared on August 26, Mr Coyne has embarked on a tour of the country to meet members.
It has recently seen him take in BAE Systems in Barrow, the General Electric site in Rugby and Marston's in Wolverhampton, as well as the Hadley Castle Works GKN site, where he is hopeful of a resolution to an ongoing dispute.
"I want to lead, but I also want to listen to what our members have to say," he says.
"It's only by understanding the hardships they are facing and tailoring the services of the union to them, that we are going to be as responsive as we need to be.
"And after what everyone has been through with the pandemic, it's nice to be able to get out and see people again."