Hmmmm.................the Slackpacks will put KDE in /opt/kde, but a creating a symlink called /opt/kde3 which points to /opt/kde is trivial..........
Slackware pkgs are nothing more than gzipped tarballs with a TGZ extension.................each pkg also has an "install" drectory which is where the package description is (called slack-desc) and an installation shell script called "doinst.sh", which sets up any symlinks needed by an application, and possibly some other configuration details..........
The main problem would be the backend configuration details...................in other words, how similar is SuSE to Slackware............enough to make it workable? The binaries themselves shouldn't be a problem, just the configuraiton...................One major difference is SuSE uses the System V style startup, while Slackware use the BSD style startup...............aside from that, you would have to know the inner workings of SuSE to figure out how to make it work.....................for a Slackware user, that shouldn't be much of a problem since he/she is used to dealing with configuration details................Not so with a SuSE user, since YaST does much of that for you................Some food for thought......
And the answer is No to your question about applying the patch after compiling.................a CPP file is a C++ source file for creating the binaries themselves..............the compiler transforms that ASCII source file into a machine readable binary format the computer can make use of..........
.....................Although, I wonder if replacing the compiled binary with an already patched one would work........