thank you for the kind and comprehensive answer!
Regarding point 1, I still have some difficulties.
Our internal Docker repository is configured in HTTPS, self signed certificate, no username, no password, so it must be called by using his name, not the IP address.
On the other side, it seems that the CF stager is able to only resolve DNS names through the public Google DNS (126.96.36.199), so when we use the domain name of our internal Docker repository, Cloud Foundry is not able to resolve it.
Is there a way to configure CF/Diego so that DNS names can be resolved by means of our company internal DNS server?