You might want to look at WebGility's Unify. They have a much better system than the add-on above that allows 2 way syncing, orders and customers. It's not cheap or without it's own issues, but we've run it's predecessor (ECC) for many years now.
I understand you, we will discuss this with managers. Thank you.
You see there needs to be change in mindset - most of the functionality that Store admin needs - vendors will need that includes sales tax, Quick book, Amazon sync, eBay sync...
For example..I took a ShipStation add-on - it said compatible with MV, but it only allows MV admin to use ShipStation. No ability for vendors to use ShipStation. Every add-on must mention ability for vendors to use it or not. In fact Marketplace needs to have check-box that add-on developer must check, it gets very confusing when they say MV compatible but vendors can't use it.