Hi Piotr,
It is very likely you will need iRules to achieve this, as I don't think the ServerSSL profile supports SNI. We basically read the SSL extension in CLIENTSSL_HANDSHAKE and keep it in the session table with the SSL::sessionid as the key (value is SSL::extensions -type 0), and then inserting it in SERVERSSL_CLIENTHELLO_SEND.
This is only a problem of course if your servers also serve different SSL certs using SNI so this solution is more for a niche problem. If your servers don't actually run SNI themselves, then sending the SNI value in the CLIENTHELLO is a moot point.
Radu