To allow vendors to print off shipping labels, ideally the labels should have 'From address' as the vendor's location. In your case, I am curious as to why are you looking to keep a single address as the from address? In addition, what would happen for the case of rates? As if two or more vendors' products come to cart, the rates have to either be added and shown or split and shown. What are you looking at here?
A solution in the Multi Carrier Shipping label app can be provided, however for that the above cases need to be answered and we would also require a few more details. For more info, you can approach the app support.