Themes should not have plugins built into them. If the theme author whats to have an enchantment to go along with his theme though, they should be released with the theme and the user would just activate the plugin to get that functionally that the theme author envisioned. I did that with my personal theme at first, and I realized if and when I would make a 'public' version of it I would have to take a lot of functionally of it to make it more universail.

Themes should be designed to be universal with no strings attached.