Commitment days - Overrides

We have certain scenarios where we would like to override our commitment days, and I'm looking for some input on how others have done that.

On of the scenario's is blanket orders with future ship dates.  Our customer expects that because they placed the order well in advance, that we'll hit those ship dates (and we should).  But when the order is outside of commitment days (30 for us) any orders can "steal" their product.

We are not using fulfillment, which may help in this scenario.  I've also considered using preferences to place these orders against another branch plant, and then somehow stocking the necessary qty in that branch for these customers.  That also would be a business process change as we are not currently doing that.