I think you're overcomplicating things?
I mean, if you're a "big name" and people know who you are and what you're about, then your format works brilliantly, people already know and trust you.
However, if you're not, then you need to be offering viewers something of real value - and you have to get to the point really early on.
Look for some vloggers that aren't huge, but are starting to get bigger. Look at their early YouTube videos, see what they do, before they start turning to the vlogging style more and more. With most of them you find that they're actually doing something other than vlogging to begin with - they're normally offering content of value to a specific audience. They get to the point of that content really quickly.
Once they've started to build a name for themselves, and start to get an audience, that's when they seem to start to add vlogs into the mix, and more and more.
I'm not saying you can't vlog from the outset... But people are fickle, and attention spans are short. You need to build an audience, and if you can talk to a specific niche and give them value very quickly, then that will help them turn to subscribers, but also consider you as someone that makes videos that are worth watching. Then you can start transitioning to a more complex video - and your audience that trusts you will know you give them value so will want to hang around... And people joining your audience will see a high subscriber count and think "if others have subscribed in these numbers, this person must be worth waiting around for".
Just my tuppence's worth as a viewer... I could be completely wrong, and I'm sure others with more experience than me will be along shortly with even better advice!