Hi Piotr,
you have to use iRule to select different SNI enabled Server SSL Profiles (with appropiate "Server Name" fields) to support SNI on the web server level, or simply use a unified Server SSL Profile that would be valid for every website (e.g. using a fixed internal SSL certificate for every internal site).
You could also try to automate the SNI-enabled Server SSL profile selection by parsing the SNI value submitted by your client and then apply a custom logic to select the right SNI enabled Server SSL Profile on the fly within the SERVER_CONNECTED event. It should be somehow possible to do so, but I haven't digged into such a code yet... 😉
Cheers, Kai