I am a bit confused about what you are proposing and I'm unfamiliar with how the biker gangs do it other than having a "probation" period?
I'm all for solid recruitment and we have been very slow and steady for years - which has worked well to get us where we are today with a strong culture. In the past I've thrown out the odd encouragement vote to a promising non-member but I am reluctant (I think others are too) to throw the upvote carrot out there as a big incentive to become a member because it can attract the wrong crowd (vote seekers over genuine stackers).
I propose to make the get to know us stage a bit more official and give folks interested a title "SGS prospects", I think if we can convert those upvote seekers into stackers that's good for the community and precious metals, just a matter of making sure they actually legit, one idea I had is having them writing their username and date next to the metals. Also if we have a bunch of these prospects we can be extra choosy with official membership