One merit might take a while to gather, but it's not unreasonable to ask before being promoted.

For the new merit sources, perhaps they could be given the guidance to focus specifically on accounts with 0 merits (and a quick review of their post history). That way new members won't get frustrated, since they should receive a merit relatively soon if their post history is "normal".

I don't think that "buying" older accounts is a problem necessarily. If moderators ban spammers, it's a lot of money to keep buying new accounts just to spam.

My only recommendation is to further limit PMs for newbies (maybe just 2-3 per week, why would anyone need more right at the start). If we focus on giving them one merit pretty soon, it shouldn't remain a problem for long anyway.