I just love Bamboo, and even being a TERRIFIC tool, I think that supporting different build tools is a good idea, since a good Continuous Integration process is all about information.
Even though I know you have Clover, NCover is a very popular Code Coverage plugin in the .Net world.
I hope you reconsider doing this, since it would be a very nice addition to an already amazing product.
Bernardo Heynemann
Developer at ThoughtWorks UK
NCover support for Bamboo is available as a Bamboo Task as of 3.1.