If the board is spam, it will be muted, locked. Locals can continue their spamming before the board is locked.
Use report to report spam posts because it's responsibility of local members who ask for the local board.
The board is in English and global moderators, current moderators who can use English can moderate it. All moderators in Bitcointalk can use English well and all of them can do this.
I think it's a great idea to get local moderators to moderate the board. Despite that the board uses English language as a language, it also uses what we call the Pidgin English. Pidgin English is a lingua franca that is a mixture between English language and other African languages. Pidgin is widely spoken in Africa and every country in the continent has its peculiar style of speaking in Pidgin. For instance, the style in which a Nigerian speak Pidgin English is different from Ghana or Cameroon despite their closeness in borders.
Nigerian Pidgin is blend with other major indigenous tribes in the country such as Hausa, Yoruba and Igbo. So, most at times, it takes an indigenous speaker to understand the conversation between them and communicate. Likewise, it will take a local moderator to be able to effectively monitor the conversations in the board as well as sort the threads in the proposed child boards.
An English moderator is not a bad idea but for a more effective moderation of the board, you need a local or native moderator.