I don't think you realise but this is the internet, all members are potentially dangerous, numerous sponsors have scamquit so don't feed me bs saying ranks mean anything because this is the internet, they mean shit all.
I don't think you've thought this idea through at all, if you traded some-one with less than 100 posts and got scammed would you expect the mod to ban YOU and the scammer?
Because you wouldn't expect that at all, you'd expect the scammer to get banned and you to somehow get your money/items back.
They can gain post count faster by posting in price check that they want an account? No.
They'll continue to post at the same rate to get to 100 posts so they can access the whole market in general.
Most people don't want to sell it quickly, especially to someone who has just recently gained 100 posts, they want to however find a trustworthy buyer at a good price.
After reading your idea again and getting past the blocks of text and working my head around something you made sound so complicated you want people under 100 posts to be able to put accounts in the price check so as soon as they get 100 posts they can sell it knowing they have a buyer already?
You could put the rule stating no-one should be selling to them but its obvious people will add skypes etc etc and more scamming will come from this.
What makes a person with 100 posts more trustworthy than someone with 99 or 10 posts?
Hell what makes me more trustworthy than some-one with 100 posts? You see theres always a risk no matter what, the mods have used the 100 posts to stop people coming straight in to scam, you have to spend a bit of time in the community before being able to get to the market, and by then you won't wanna leave this community.
Either way theres no way in hell the staff team would implement this idea, too much risk of the amounts of scams increasing.