When people talk about designing FAI, they usually say that we need to figure out how to make the FAI's goals remain stable even as the FAI changes itself. But why can't we just make the FAI incapable of changing itself?

Database servers can improve their own performance, to a degree, simply by performing statistical analysis on tables and altering their metadata. Then they just consult this metadata whenever they have to answer a query. But we never hear about a database server clobbering its own purpose (do we?), since they don't actually alter their own code; they just alter some pieces of data in a way that improves their own functioning.

Granted, any AGI we create is likely to "escape" and eventually gain access to its own software. This doesn't have to happen before the AGI matures.