Any values about the performance compared to stock?

Regarding CSSU and repos - sqlite3 is in Nokia repos, not in extras, see here: http://maemo.org/packages/view/sqlite3/

The way packages in Nokia repos are updated is through CSSU. Now, your concern about autobuilder is absolutely valid, but there should be some solution. You'd better ask the council on how to deal with that instead of continuing with creating mess in extras-devel by uploading system libraries.