Hi Houcemeddine,
I'd love for Entity Schemas to be used more widely to ensure the quality of our data. That is still severely hindered by the ability to link a class to a related Entity Schema via a statement - your point 1. We have https://phabricator.wikimedia.org/T214884 for that and I'll bump it up in priority again. We tackled it in the past but had to take some steps back and rethink it. That being said I don't envision constraints to be replaced by Entity Schemas but rather augmented.
Cheers Lydia