This release adds full support for vanilla parity for command selectors! This now means that any (player) selector or specification that's possible in a vanilla command now works for essentials commands as well. (Note this does not include @n or @e, as Essentials commands are fundamentally incompatible with such selectors.)
Unfortunately, the code under the hood for this plugin is still pretty rough overall, and unfortunately there is still no tab completion for the selectors, but I hope to address both of these issues down the line.
Thank you to xgioa, wrjgrrgpmc-hash, and hellfirehd for their reporting and feedback!