"feels like Vim, just different enough for you to be frustrated" is true, but I like the Lua built-in: it's a fantastic language for this kind of thing, and feels more inviting to a new plugin-writer than, say, Vimscript might.
If you're after something lightweight, similar enough to be vim to be useable, and lua built-in checkout vis: https://github.com/martanne/vis
The structural regular expressions are also pretty interesting.