Their appointments come after former Samoa and one-test Kiwis forward Willie Poching and Australian Justin Morgan were not retained after assisting Kidwell through last year's poor Four Nations campaign.
"The appointments this year right across the board are just a perfect example of pathways being closed to New Zealand-based coaches," said Blackmore.
"I've never had an opportunity to coach a New Zealand representative team and I've been banging that door down the whole time. The messages are mixed because they're constantly saying you need to be on a coaching, managerial, or player pathway but then nothing actually eventuates."
Blackmore has no doubts about the credentials of McNamara, Richardson or Green but believes their appointments raise further questions about Kidwell's ability as a head coach.
"Don't get me wrong " we all need help," he said. "You might bring in a forwards or backs coach if you feel they could add something to the mix.
"I'm not saying they aren't good coaches, that's irrelevant. It contradicts everything they are saying and they've been saying this stuff for far too long."
Blackmore began coaching in 2004 and enjoyed success at club level with Manurewa and Otahuhu and the NZ Maori before winning the New South Wales Coach of the Year award in 2011 after guiding the Auckland Vulcans to the NSW Cup grand final.
After a year in the UK working as general manager with Leigh Centurions, he returned home and applied for the NZ Residents under-18s job but was ruled ineligible because he wasn't on the NZRL coaching pathway.
A return to coaching with Papakura in 2014 put him back on course and that year he was among the final four applicants for the Kiwis head coaching role, before Stephen Kearney was eventually retained and Kidwell introduced as an assistant.
Despite making the shortlist for the top job, Blackmore was again overlooked when Kelvin Wright got the nod as analyst ahead of the Kiwis successful 2014 Four Nations campaign.
"This is where I started to get disappointed in the process and procedures the NZRL were employing," Blackmore said. "I got shortlisted and then couldn't win any role. No pathway was extended to me."
After coaching the Sea Eagles to their maiden Fox Memorial title win last season, the 47-year-old is unsure of what more he can do to advance his career after recently being told a poor interview meant he was denied the chance to coach the Junior Kiwis, with Australian-based former Kiwis World Cup winning captain Nathan Cayless getting the job.
"The big shame is that I think I'm a good coach and I've gone a long way to having a good sound understanding of the game but ultimately I've got to the point where I have thrown it in.
"NZRL have lost a good quality volunteer because they've shown me no support.
"We must have some people in New Zealand that deserve an opportunity."
NZRL boss Alex Hayton would not comment on Blackmore's grievances but insists every effort is made to develop and promote local coaching talent.
A review following last year's disappointing Four Nations campaign revealed the need to provide Kidwell with more support and McNamara and Richardson's appointments have been made with the aim of ensuring the Kiwis have the best chance of performing at the World Cup.
Green's involvement with the Kiwis is not confirmed and Hayton says the opportunity remains for a New Zealander to claim an assistant coach position later this year providing they have the right skills.
"If the focus is on winning the World Cup then we have to put the right people in to do that," said Hayton.
"That is the focus for this year. The long-term focus of having an assistant coach who is a Kiwi that we're looking at for the future is still there.
"If there's someone that fits that criteria going towards the World Cup then fantastic but if we don't we're not going to compromise by putting the wrong people in at the wrong time.
"When we get through the World Cup and then start looking forward to the next few years we will be looking at who out there as assistant coaches is a future New Zealand head coach."
Hayton argues McNamara was a logical choice to assist Kidwell due to his role as Warriors assistant coach that sees him working weekly with the Kiwis spine of Issac Luke, Shaun Johnson, Kieran Foran and Roger Tuivasa-Sheck.
"To bring those players in and bring someone else in to work with the spine, that doesn't make sense when we can get someone who's working with them each week," said Hayton.
"It's not saying that David can't do the job but it's getting the right balance in skill sets in that management structure to get the best results out of all of the players.
"And that's why we haven't made that other assistant coach appointment as yet because we want to get through this week, see how it all runs and 'do we need anyone else' and if we do, what role are they playing?"
