Trust your Citizen Developers. Educate and Empower them. Be supportive. Citizen Developers don't want to create a mess any more than you do.
By locking the core Rulesets (and thereby requiring Branch development settingsbe in force to make any changes), that immediately contains any "damage" to Branches which don't form part of the deployable application until a professional developer in Dev Studio has authorized those changes be merged.
Conduct frequent (daily) Branch Reviews with newer Citizen Developers, identifying rules that have landed in the wrong branch, class or ruleset. Agree the sequence of events that contributed to this outcome, and agree an alternative approach. The error rate will reduce over time and your Review frequency can reduce as confidence grows.
The end result is an empowered, trusted and self-sufficient Citizen Developer squad that pushes a high quality product forwards and ultimately frees you up for critical architectural decision making and professional development.