Personally I would suggest that you keep the vmware modules separate from your kernel package. Either make a separate package for vmware or just use its uninstall routine (and pay attention to the uninstall messages as it won't completely uninstall itself).
The official Slackware packages keep kernels and modules separate as well. So, if anything, you would be adding the vmware modules to your custom modules package. If you do want it all in one big package it is very easy to manually make this package.
Kernel and module files are so easy to install/uninstall manually that I question the usefulness of making custom packages for them in the first place. You just throw three files under /boot (optionally change the symlinks), your modules folder under /lib/modules, add a /etc/rc.d/rc.modules* file, and edit and run lilo. The last step, of course, cannot be a part of the package, so you will always have some manual work regardless.