I've seen many bugs that (because they had a workaround) were pushed away because nobody had the mental strength to open their specific can-o-worms or dig for their root cause. Someone who comes in just for those sounds like a sweet deal.
Because in many cases fixing those requires understanding the whole working model of the system in it's whole, you now have established a relationship for future bug elimination. And the next bugs will take less time as you now have that mental model...
All in all - good niche idea, if you can find how and where to market it.
All in all - good niche idea, if you can find how and where to market it.