Hi,
To answer your questions:
1. I assume you mean having clustered Blackberry servers? If so this is not possible. As an alternative get a product like
Neverfail which can instantly failover your BES to another server on or offsite.
2. If the RIM servers go down you can't access email or if you local internet connection that your BES uses goes down you can't get emails.
3. If the BlackBerry SIM is removed from the device you can't remotely wipe the device. It is best practice to enforce passwords via BES I.T Policy as a lost or stolen device will self erase after 10 failed password attempts.
Thanks,
Gary