A serpent is on the maybe list, I'll pass on the shrimp as they make target feeding this many corals a challenge.
The open top further restricts fish choices. If anything a couple nano fish such as cardinals or a pair of Picassos and an RBTA (added long after the tank matures.) I created a perfect environment for an Anemone in the center pillar, just not sure I'm willing to give up that much space and deal with the possibility of it going on a "road trip".
even though the shrimp may eat the food it may be a better benefit in a small tank to have him than to not have one. i have a peppermint in my 2.5g nano because he eats all the food that does not land on my coral so they do not turn to nitrates. what i do first is find where he is at and i will shot a piece or 2 of shrimp at him to keep him occupied for 10-15 minutes while i feed the coral, then when he is hungry an hour or couple hours after he goes and eats what the coral didn't get. Just some food for thought!