There are multiple responses to this suggestion.
Support for SQL-like syntax for UPDATE, DELETE and INSERT INTO are not on our road map at this time.
However, the underlying functionality for an UPDATE, SET is essentially a PATCH. This functionality we are actively working on. See this User Voice item here to track for future updates. https://feedback.azure.com/forums/263030-azure-cosmos-db/suggestions/6693091-be-able-to-do-partial-updates-on-document
Thank you for your suggestion.
We understand this is a top customer ask and as such it is currently on our backlog to be prioritized. We will update when the status changes.