A plugin that lets you quickly and easily create new themes.
Nope, not in the slightest. You have been warned.
That said, it's perfectly "safe", given a certain definition of the word "safe". The "create a new theme" screen itself is secure, and inaccessible to anybody who lacks the capability to "edit_plugins" to begin with. Themeinception also uses the proper WP_Filesystem methods to create the theme files, so there's no worries about incorrect file ownership on shared hosting. You may have to give it FTP credentials on some hosts for it to be able to create the theme, that's the WP_Filesystem at work, making sure the files are correctly "owned".
All this plugin really does is make it quick and easy to create a new one-off theme and take you directly to editing it. Cowboy-coding at its finest.
The pluginception plugin by Otto42 inspired me
Then modify the plugin however you like to do whatever you want. Don't bother me with it. This plugin does what I want it to do.