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Ok... hive already allows custom JSONs which is almost like a generalist way to allow "smart anything". Then the layer 2's can implement smart contracts, Hive-engine is one of them, but there are more layer 2's running on top of Hive.

Running smart contracts at layer 1 is kind of pointless... and very expensive. You want layer 1 chain as simple as possible, as secure as possible and that is for a very good reason, because of scale and transactions cost. If you keep adding stuff into it, (aka look at EOS for example), it becomes very complex and expensive to support, maintain and therefore decentralize.

There is a reason why "dumb" chains are sooo quickly expandable (aka Bitcoin).. its because effectively to run them, its relatively inexpensive... just to allow you to send/receive transactions and or even validate blocks. To produce is another thing... but even then, you can do it very cheaply.

Sorry not replying sooner, but for 3 times I was trying to answer you and either something broke (computer) or I got urgent stuff and then forgot I had the reply open, and eventually lost it.

Which are the other Layer 2 run over Hive? That will be an interestung post.