The proposals need to be approved by the BBC Trust
The BBC's audio and music director Tim Davie says he is "passionate" about 6 Music, but has conceded the station should still be axed.
In a blog post, Mr Davie said the BBC "didn't arrive lightly at the decision", but he was "confident" the plans would work.
On Tuesday, the BBC's director general Mark Thompson announced the proposals as part of a long-term shape-up.
He also suggested Asian Network and several websites should close.
"In radio, we're proposing bold steps to strengthen and simplify our station line-up," Mr Davie said.
"I do not believe that offering the current range of nine stand-alone digital networks is the right way to serve audiences and ensure radio remains strong in a digital world. And, while digital radio has seen growth, my concern is that current development remains slow.
"So we are proposing to reduce the number of stations and re-invest in our five core networks."
He said that only one in five adults have heard 6 Music since it launched in 2002, and less than one in 50 people listen each week.
"We could invest heavily in marketing to try to address this, but my preference is to ensure that money is focussed on unique, high quality radio, not supporting a large number of services," he said.
"I know that there is real sadness that we are losing valued services, but this is part of a strategy to ensure BBC Radio continues to be as relevant and popular as ever in the digital world."
The proposals will go through a public consultation before being approved by the BBC Trust.
On Wednesday, the trust's chairman Sir Michael Lyons said "public concern" might mean the BBC will have to "rethink" its plans.
There has been criticism from several members of the music industry about the plans to close 6 Music and Asian Network.