As of RouterOS v6.14, SSH with the None cipher is supported. This was a feature Mikrotik implemented specifically because of HamWAN's request.
The attached diff file can be applied against the specified version of OpenSSH so that an encryption-free ssh client (and server) can be built.
Apply the patch
cd openssh-6.6p1 patch -p1 < ../openssh-6.6p1-HamWAN.diff
Compile the rest of the package as usual, to your taste. Be sure to set "NoneEnabled yes" in ssh_config and/or sshd_config files, depending on where you would like to support the none cipher (client and/or server).
Use encryption-free SSH
# Do authentication using an encrypting cipher, and once authenticated, switch to the None cipher ssh -o NoneSwitch=yes host # Use the None cipher from the start, including during the authentication phase of SSH ssh -c none host