The only argument for putting out policy early that carries weight for me is to help "define" an unknown quantity. Opposition leaders are, in many cases, blank slates, barely recognizable to the average Canadian, so you could argue pumping out policy gives shape, definition. Even in this instance, there are plenty of pitfalls in releasing too much "substance", because truth be told your audience is distracted and your opponents are keen to corner, label, define themselves. A certain ambiguity does have upside, after all the role of opposition is to oppose, not lead. It's a tricky proposition, what to release, how much to release, pros and cons, no question.
Justin Trudeau is not the typical opposition leader. We have "known" Trudeau since he was a kid, he has been in the public eye throughout his life. This reality means many had opinions of Justin, good and bad, prior to his ascension to Liberal leader. In other words, Trudeau doesn't need to "introduce" himself to Canadians in the traditional sense, his celebrity is unique in this regard. Within that then, this idea that Trudeau must put out policy is somewhat a non starter for me, because many of the arguments don't apply here.
Stephen Harper came up with FIVE ideas in the 2006 election, it took onservatives 13 years to develop this scant list. On top of the miniscule platform, some of it was simply gimmicky, knee jerk counters to highlight government Achilles heels, not a deep philosophical treatise. I seem to recall Harper becoming Prime Minister, as I also recall "policy wonk" Dion getting hammered. Justin Trudeau would be wise to ignore the media, comforted in the fact only diehards are engaged and the real fight is many, many months away. Build the team, build the organization, pump up the fundraising, develop the platform behind closed doors, look credible in opposition, when the election nears, that is the time, certainly not now.