I would like to test building a factory with bots. Since the blueprint sandbox instantly builds ghosts, instead of adding a creative mod, going back to nullius and building all the initial blueprints first, could a game/player option be added in the blueprint sandbox to disable ghost auto-building?

As a current alternative, you can adjust the asynchronous settings such that things basically aren't built for a while - for example with handling only one request at a time and every 30-seconds.

This is introduced in 1.18