Is it permissible for the regular Imam to continue his imamate if he is forced to make congregational supplications after every prayer, threatened with replacement by another who may not be upon the Salafi methodology, knowing that his continuation may benefit the worshippers through his sermons and methodology?

Authentic hadiths command certain supplications after prayers, among them the Prophet's instruction to Mu'adh: "O Allah, help me to remember You, to thank You, and to worship You in the best manner." This applies if the supplication is individual. However, gathering for supplication after every prayer is an innovation (bid'ah), because it is an invented method in religion that rivals the Sharia (definition). If what is sought is merely individual supplication, there is no objection, but it is better to sometimes omit it to avoid controversy.