There are two main roles offered by the centosplus kernel; one is to provide features that are disabled in the distro kernel and the other is to fix known issues by applying patches. The plus kernel for .el7 is now under development and can be followed in this bug tracker.
So far rebuilding the kernel with modified config file(s) seems straightforward — at least not as convoluted as it is in .el6.
A number of drivers have been removed / disabled in EL7beta compared to EL6.5 as seen in the EL7beta Release Notes. They are good candidates for the plus kernel. A user who needs the ath5k driver realized it wasn’t in the el7beta and rebuilt the kernel. This and other drivers will be included in the .el7 plus kernel.
At some point, a test version will be made available, so stay tuned. In the meantime, please file a request for features and propose bug fixes by opening a new bug tracker report.