To reduce the size of the image, I suggest to use OpenVPN 2.3.x with PolarSSL. You could save more than 1 MB.
To build PolarSSL as a shared library and reduze its size, please look at the patches at http://freetz.org/browser/trunk/make/libs/polarssl/patches
To be honest, I didn't check if other binaries depend on OpenSSL, but they can hopefully be ported to PolarSSL, too.