Yes, you can add on to your original contract at a different home resort.
You would have 11 month booking privileges at both home resorts, but only for the amount of points owned at each resort. You cannot combine points until the 7 month window.
For example, if you owned a 160 points contract at AKV and added on a 50 points contract at VWL, you could use the 50 points at VWL when the 11 month window opens, but could not use the AKV points at VWL until the 7 month window opened. But if you bank and borrow, you could have up to 150 points to use in the 11 month window at VWL every third year..