To generate a vimball file for your vim plugin isn't very hard. You can use vim-makefile to generate vimball file automatically.
to get vim-makefile:
$ wget http://github.com/c9s/vim-makefile/raw/master/bin/vim-makefile
to add makefile for your plugin:
$ cd plugin
to make your vimball (place your plugin code in vim runtime directories, for example:
then run `make vimball`:
$ make vimball
then the vimball file will be generated.