Here's an simile to what i'm saying
If cigarettes are like cooking then eating a pizza.
vaping is like eating a pre cooked pizza that is always in arms reach that regenerates after each bite for a few hours.
For some i could see your visceral emotional response with not having an infinite pizza anymore but for others miss the waiting for the pizza to cook (waiting for when they feel they need a cigarette rather than vaping throughout the day randomly) cutting the pizza into sections, taking the first bite and being able to finish the pizza and feel that "ahhh" feeling.
I see your point, but this is a somewhat inappropriate comparison. You are comparing two different scenarios using the same exact object. Vaping and smoking cigarettes are completely different.
Here is the issue. There is no exact vapor to analog smoke ratio established. If you wanted to create a device that would limit a users puffs to equal the exact nic absorption as a cigarette, you would need to establish constants for multiple variables. The device would also need to fire for an exact amount of time with no variation, know the exact cigarettes you used to smoke, and know personal things such as body weight to calculate how much nic is needed. Bio-availability between the two different delivery forms, and more importantly, the exact amount entering the blood stream per hit and how this absorbed nic reacts in the body over a certain period of time, lets say 5 minutes for arguments sake. One person hitting an ecig might need to take 50 hits in 10min and 20 in 20 minutes for someone else to get the same effect.
My point is, this is all about knowing your limits and having self control. There is no end-all established data due to variations in different people. New users need to figure out what satisfies them, and at that point try to control their vaping. Your idea, in my opinion, would do nothing but result in frustration and non-satisfied users or over consumption because the device is telling them what to do.
EDIT: Also, by your suggestion and comments, it seems that you never experienced a time where you needed more than 1 cigarette in a sitting to satisfy you? Or a full cigarette was too much so you put it out before it was finished? Everyone is different and no device can factor in all the variables. Sometimes I would smoke 3 cigarettes in a row before I was satisfied, sometimes I couldn't handle more than half of one. I don't think there is a person in the world that would smoke exactly one cigarette to exactly the same point every single time they have one. It's just not realistic in real-world scenarios.