I was going with my diea towards the model of most of the apps, where you can introduce all sorts of stuff of lotery like inventions, that are great at sucking the money. Everyone loves it, so its an easy way to increase the revenue.
As for your proposal - it would never go through. Why someone should pay 2$ to read novel with 100 chapters locked while he could use it to read novel with 2000 chapters?
And well, that would give everyone access to something WAY MORE EXPENSIVE than this 2$ or even 10$. What I though about when reading your post is below:
Catch Up pass - unlock specifically for a single novel alone, allows you to buy all its current premium chapters (outside of priveledge and let's say, most recent daily release) for 50% of price, but it can only be used if you never got this tokenon said novel.
Daily Update pass - unlocks all daily chapters for a month, for 75% of estimated total cost of the chapters (something like privledge, if novel has 2chaps/day, it will unlock 2 chaps per day for you, but if author does mass release, you would've to catch up with those bonus chappies by yourself.
Overall, I think this is better proposal, because 1 - the price depeneds on the amount of work someone had to put in order to get his current amount of locked chapters, 2 - limited time reading will never work, because varoius people have varoius reading speed and lets be serious - you can't properly calculate the average cost of the entire premium novel on the site, with how some have 1k chapters while some have 50.