the tank looks really nice. I've never had shrimp but have always wanted to try them. I think I'd give it a go in this tank since you have the room.

The only concern is for the assassin snail. if there are no snails in there you need to feed it. It's my understanding they do not eat algae that grows in the tank, but they will eat algae wafers. They will also, if really hungry, eat baby shrimp .... so keep that all in mind.
Maybe you could trade the assassin for a mystery snail?