In an effort to get more use of UDFs and at least some plugins, this is an idea to make these "safer" in a way that they don't crash the server even when they go wrong. The way to achieve this would be to run said UDFs / plugins in a separate process with the same UDF / Plugin interface as MariaDB Server and that communicates with MariaDB Server by some means, likely proprietary, likely through a Unix Domain Socket or similar lightweight mechanism.
MariaDB Server would be responsible to start this separate process if it is not already running and then pass any data to it that is necessary. If it doesn't crash it can keep on running, if it crashes, by virtue of bad code in the UDF / Plugin, it will be restarted as necessary the next time it is needed.