Why not go ahead and help them? I'm sure they'd be happy to have the assistance. Fork mongo from github at https://github.com/mongodb/mongo . Happy hacking!
(It's a nice opportunity to publicly show off a specialty/core competency and brush up a bit on C++ a the same time. I'm not that easily provoked into action by internet commentary! ;) )
But, looking at the source, I think I will be probably a Bad Contributor and end up with a gigantic pull request and a (mostly) full re-implementation...