Effect stage and Overlay by vanilla mobs

Sorry if wrong section. 

Questions: 

Is it possible to separately track "progress" for the effect on the player? Since nbt tags seem to work, but the topic about "not very synchronized" is puzzling. 

Is it possible to somehow teach vanilla creatures to impose new effects on the player? 

Detailed: 

The idea was that the player would be able to catch some negative effects. Which will gradually increase over time. At the beginning, for the effect stage, I thought to use a global variable, since the idea on the player could be current 1 active effect. Now the player can catch several of these effects, but it turns out that if the effect on the player reaches stage 2, the new one received will instantly reach stage 2. There was an attempt to use spell power as an effect stage, thus making the progress of several effects separate, but there were a decrease in the stage due to the peculiarities of the spells and the code to cancel the treatment with milk. And the NBT tags worked, but they give out a warning .. And it's not clear how to fix it or do it right. After all, the mod is made for the server.