Not that I particularly endorse this practice, either, but your way wouldn't work. You're missing the part where the reward for hard work is more hard work. You definitely can get promoted this way, but, you can't really use it to maintain a whole other job, IMO.
That's why I said you define the niche and overstate its work. You work hard and build trust and then yes if you ask for more work, you get more work. However there is a window in which to define what you do next and make it seem like more work than it really is.
I don't really understand what you're saying. Is it that you need to say "I'm really only capable at $THING, but $THING is very, very important/takes 2x more time than I'm actually saying it does?" If so, I don't understand how you hope to BS all your managers and coworkers into believing either of those things.
