How to set the Revenue territory copying it from the related account?

Summary:

We would like to use redwood forecast based on territory and opportunity amount.

Unluckily it is not possible, so as a workaround, we are developping a groovy script that copy the account territory into the opportunity revenue territory.

Moreover, in order to be sure the sales have enough authorizations to set the territory in the revenue items, we would like to use a Priviledged function, but it is not possible due to a "Required Permission missing" error.

Content (please ensure you mask any confidential information):

Redwood forecast, based on territory, requires that territory is set in the opportunity revenue.