I think that any blockchain ecosystem needs the ability to create smart contracts (think DeFi). Hive-Engine in it's current form is not robust since it's basically a centralized token issuance entity.

Having said that, it is my belief that implementing atomic swaps at the core level is more important than second layer solutions.

Deploying a smart contract platform is a big deal (even on a second layer). You have to decide how to handle buggy code beforehand (you don't want an Ethereum DAO like incident) and so much other stuff to think about.