"It was announced yesterday certain sections of them are going," Peters said, evoking a few cheers from the audience.
"Now I'm sorry for some of them because they deserve to stay, but for some of them: good riddance."
The comment appears to have been a late decision, too, not appearing in his official speech notes.
Peters later dug in, saying it was positive some people at the organisation could lose their jobs.
"There are some superb people who work for MediaWorks but I won't tell you who they are."
Peters has framed the conference as the start of the party's march towards the 2020 general election and a key plank of its strategy is trying to appear a neutral force between Labour and National.
His speech – like last year's – was scathing about the latter, calling its 2017 campaign "tawdry" and pointing back to Steven Joyce's "$11.7 billion hole".
"That's their last outing. Don't give them, unless they reform, another chance."
He later explained to journalists "no party is beyond redemption", but continued jabbing at the Opposition.
Peters also took time to talk up his party's achievements as a brake on the Government's policies.
Describing Capital Gains Tax as "economically damaging", he said NZ First had stopped "1970s-style" industrial relations rules, and won concessions on climate change regulation.
The start of the weekend's conference also marked exactly two years since Peters announced he would be forming a Government with Labour.
In the second headline-grabbing moment of the day, Peters briefly left the convention to speak to a group of gun-owning protesters assembled across the road.
Armed only with picket signs, the protesters say they feel "persecuted" by the Government's latest tranche of firearms legislation – which includes setting up a register - and are calling for NZ First to block them.
Peters - accompanied by Government Ministers and avid hunter Ron Mark, and Shane Jones, who was this month photographed with an AR-15, the type of assault rifle used in the March 15 attack - made no concessions.
But he told the frustrated gun-owners his party was keeping an open mind about the law through the on-going Select Committee process.
Inside, the party went about its annual work – including the process of publicly debating policy suggestions by members.
The "remits" aren't automatically party policy but are sent to be decided on by the party's parliamentary caucus of nine, including Peters himself.
Among the dozens of policies debated in rapid succession was for a request for the party to investigate bringing in 100 hours of compulsory community service for all people aged 15 to 19.
Other proposals included supporting an independent review of the Auckland Supercity and trialling methane-reduction technology including GMO ryegrass.
The party's youth wing also managed to convince members to consider a remit supporting quality-testing of pills at music festivals. However, time expired before the topic came up.
Police Minister Stuart Nash has been keen on the idea, but Peters has argued it could encourage illegal drugs use.
Members voted down proposals including making vaccinations compulsory for school children and increasing the drinking age for off-licence to 20.
The morning began with a video tribute to former member and Ngāti Hine kaumātua Pita Paraone, who died in August.
Guest speakers through the day included Business NZ chief Kirk Hope and Rotorua district councillor Tania Tapsell.
Peters will on Sunday announce a new party policy when he makes his keynote speech, expected to run as long as 40 minutes.
The party will also reveal a replacement for former president Lester Gray, who last month resigned in a letter citing concerns he had not been given enough information about the party's financial documents to sign off on them.
NZ First acting president, Jude Patterson, Peters, Gray and senior MPs have declined to elaborate on the resignation.
Members John Hall, from Manurewa, and Kristin Campbell-Smith, Rotorua have put their hands up for the job.
