But, looking to consider a path/level scenario with power-ups (free letters/vowels/slowdowns/etc) or implement that interface into a different style of game like Papers Please or similar.
I like the idea of having this as a mechanic within some other meta-loop (Like your Papers, Please suggestion). That allows you to expand the game design beyond the scope of this (already demonstrably good) mechanic without needing to change and balance it.