Packaging library distribution

I'm working on some shared library and now stuck with the problem that some software refused to pick the newer version, but some has to use the latest since it has some crucial changes. So I need to keep 2 different versions of the same library. The problem is I use sort of "fat" package libel.deb that contains header files needed for developers as well as the actual binary so compatible with the header files. I'm thinking of splitting the libel.deb into libel-dev.deb and libel1-bin.deb, libel2-bin.deb. But the problem is the libel-dev contains headers compatible with le latest version of the library so developers actually need to install 2 packages: libel-dev and libel2-bin which is error-prone (very easy to install incompatible dev and bin packages). How to go about this issue? Probably it is possible for dev-package to contain binaries as well...?