What you are suggesting will only benefit account farmers more than the forum. nobody wants to pay you more money, all of the campaigns based on stakes are not paying you any thing from their own money, they are paying you with other people's money.
Expecting merits for doing a long post with graphic is not meritorious. if you really want to contribute, spam bounty managers with your OP, see what happens. paying less to members with no merits will create a market to buy merits to get more in a campaign.
Merit exchanges have occured (and it is not strange due to basic human instinct) regardless of campaigns required merits to get higher payments or not. Simply because lower ranked users need merits to rank up (particularly shit-posters who are unable to write high-quality posts and will never get merits by themselves). Merit exchanges are very popular in local boards (I saw lots of users pointed Russian out as the local board massively abused merit system).
I strongly support ideas of signature campaigns to pay higher rewards for users who meet their merit requirements.