Executing after you're dead only happens once, so it can be heavyweight.

Updating should be as lightweight as possible. One reason it's heavyweight in the current system is that, after you're dead, people who didn't get what they think they deserve can sue your estate. Often the argument is that you were under someone's influence when you updated your will. Having your estate lawyer say, "Mr. Disruptthelaw came into my office on ___ date and we discussed this amendment. He appeared to be of sound mind" is fairly persuasive to a judge. But a late-night edit to some database, even if it's on the blockchain signed with your private key, might be less convincing.

The usual way to work around the difficulty of amending a will is for the will to say "Everything in the Disruptthelaw Recovable Living Trust is goes to ___". You can move assets into and out of the trust easily.