But as the party seeks to rebuild its core, the party board may also be keen to keep the type of role former leader Rodney Hide had as Minister for Regulatory Reform.
He was also Local Government Minister but that has been ruled out by Mr Key as inappropriate given that Mr Banks sought election to the Auckland Super City mayoralty last year.
Mr Banks also answered questions about the teapot tape - the recording of his cafe conversation with Mr Key thought to have included a reference by the Prime Minister to New Zealand First voters dying off.
He said he did not believe the publicity New Zealand First leader Winston Peters got from the tape had any impact on his success at the election.
He had believed for six months that Mr Peters would return to Parliament.
"The tea party was useful," he told reporters "and the work you did for me on behalf of the tea party by giving me every opportunity to promote the strategic vote was very helpful and I'm grateful for it."
Mr Banks was accompanied by former Act deputy leader John Boscawen in his talks in Mr Key's Beehive office.
A deal with Act and United Future leader Peters Dunne is expected to be clinched by Thursday.
The Maori Party negotiations may be slower.
A large contingent arrived, initially including co-leaders Tariana Turia and Pita Sharples, their political advisers, Waiariki MP Te Ururoa Flavell, party president Pem Bird and vice-president Ken Mair.
Mrs Turia and Dr Sharples left the talks part-way through leaving Mr Bird and Mr Mair to run the show for the party.
Mrs Turia said there was nothing untoward in them leaving the talks in favour of the party leadership.
"We think it's their place. We work for them and they've got certain expectations of us and are very clear about what it is they want us to achieve so we have left them to negotiate."
National does not need the Maori Party at this stage with enough votes from Act and United to have 62 votes in the 121-seat Parliament.