You mean 0-100 from being a vassal, over time, but limit the 'Improve relations' from 200 to 100?
Mhmhmh, I'm afraid that can't be done. Keep in mind you occasionally have to overcome -40 heretic neighbour, -15 has claim modifiers of your own vassals. If you only get 100 for vassal, 100 for diplomats and 25 for a gift, you cannot always reach the 190 necessary for annexation. This means people would have to intentionall declare wars, have their vassal sieged, then unsiege them to get that relation.
The Improve Relation should, at least, give up to 150, or it won't work out in special cases.
My math failed. Yes, improved relations up to 150. It should be possible to reach the same positive modifier we have currently.
Afaik I already described something like this, but I'll go back and make it more clear if it's not that clear.
To be honest, I didn't read the whole thing, as I'm doing other important non-eu4 related stuff here. The topic and TLDR just sparked enough interest to comment and give support.