Stephen McNeil is the only Liberal in Canada right now with the profile of a 'fiscal conservative.' I predict the next Liberal leadership race (the sooner the better) will be between 'Red Liberal' Chrystia Freeland and 'Blue Liberal' Stephen McNeil.
Canada has not had a Premier lead a Federal political party since Bob Stanfield led the Progressive Conservatives. Dave Barrett came close to winning the NDP leadership in 1989 but by then he hadn't been Premier of British Columbia for 14 years anyway.
The Progressive Conservative leadership race won by Stanfield in 1967 was something of a star packed field. In addition to Stanfield, Manitoba Premier Duff Roblin also ran as did former British Columbia Progressive Conservative leader Davie Fulton (though things didn't work out for him provincially.)
Unfortunately for the P.Cs, John Diefenbaker also ran to try to hold the job. I can imagine he made the convention something of a nightmare.
I don't think McNeil has any aspirations to run federally. Could be wrong though I guess.