@Bellingcat This is totally a nerd snipe! It sounds like such a simple question yet it's a really hard. What's 1) Important 2) Visible from space 3) Isn't already routinely imaged.

Without directly answering your question, I think I'd be most interested in indirect economic indicators that check on regimes that predisposed to lie about their economies. Perhaps something like amount of logging activity in Russia or construction activity in China.