In the Hindi language there is an equivalent phrase which is widely used when a common man who is trying to suggest an idea to a person in power or some higher authority respectfully without challenging the latter's incompetency to 'not see the flaw' in the system. Example: A head of the police department being addressed by a common man (person of a lower stratum) giving an intellectual suggestion. I have translated a suggestion which was originally in Hindi.
Common man: Small mouth big words but Sir, wouldn't it be a better idea to install wireless communication systems in police station too?
Is this phrase used in a similar fashion in English too? The only phrase I have seen is 'in my humble opinion' used at the start of sentence in such cases. Another phrase I know is 'Small mouth, big talk' but I haven't seen it used as a prefix in sentences. Any other appropriate suggestions are also welcome.