Hive Engine is very easy to code for, everything from token transfers to staking to market orders is done as smart contract interactions triggered through custom json transactions. And we already have NFTs, which have been used with great success as the building blocks of the dCity game. :-)

We are busy extending the basic smart contract offerings beyond simple tokens & market contracts. We now have an automated market maker contract which anyone can use (see this post), and several other new smart contracts are in the works. I'm currently working on one called packmanager, which can be used as a Splinterlands style mechanism for opening packs of NFTs. And a new mining contract is about to become operational. The aim is to provide a robust toolbox of smart contracts that developers can use to easily add different features to their tokenized applications.

As far as robustness, we have not had any major problems with the sidechain since launch, and if something were to happen to the node we could just do a chain replay from the latest snapshot point. Introducing a decentralized witnessing system is a major goal in the short-to-intermediate term, and discussions around how best to go about that process are starting to kick off, as I think you're aware.

TL;DR: SMTs will be great I'm sure, but everything they will offer already exists in the form of Hive Engine fungible tokens, NFTs, and smart contracts. Why wait for a layer 1 solution that has been delayed for years, when we have a layer 2 solution now that works great?

When SMTs do launch, I'm sure we will have ways to have synergies between them and Hive Engine, though what form those synergies might take is yet to be determined.