A very good Wikipedia article will be equivalent to a review article, but such an article isn't a meta-analysis: it doesn't include only studies which can be boiled down to a few summary statistics like d. There's also little way of being sure that the article is comprehensive and unbiased - one reason meta-analyses usually make a point of how they did a big search on Pubmed and looked through hundreds of results etc.

I don't know what features could be added to deal with either problem. Any meta-analyses tucked into WP articles would be rightly considered Original Research.