Hi Richard!
X-Cart Multivendor currently is a single warehouse. We plan to extend this package, so it would allow vendors to ship goods from different locations, but we need changes to order system and they will come in 5.2.
It will be changes discussed here:
http://forum.x-cart.com/showthread.php?p=379394#post379394
So, your suggestions are great and we do want to implement them.
As for vendor's address, it is always good to provide some info about vendor rather than not. It is just nice thing to have.