If you are marketing your product on a large scale, I suppose you must be creating your creatives based on your rules and regulations of your brand book and then distributing them to various vendors associated to you. This is done to maintain the consistency of your brand and easy recall to customers viewing it on different platforms. However, if you are working on a smaller scale, you can authorize a vendor for creative development and assign a person from your team to give final approvals as per your brand ethics. But design and development of creatives will be charged as extra.