I can offer this but it is not fool proof. When the site is uploaded it makes a backup in that directory online.
If you both download the latest vnu backup and work on that but only on the page you have agreed on. That will get the site done, however once finished one of you will have to go through the complete site to check for errors.
VSD is a quick way to create a viable site but I agree it is a one person deal. I hear all the time that the site has to be finished tonight. Well I am afraid that the only way to create a viable site is with planning.
The best way is to sketch the pages in an exercise book of element placing, content of each page. page names, meta information, any clever displays etc. Then the actual page can be build using that guide. I cannot imagine trying to do that first in a blank VCD page or coding in a blank html page. It would be all hit and miss hoping for a result Eeek! Trying to use VCD or the editor to plan is not a plan.
With a layout that can be adjusted and with the logic that can be followed page by page in an exercise book it makes building the first draft of the actual site so much faster and the site will tell its story so much better.
Still I guess others may have a different view. I believe doing without a plan is not the best option. Bit like cooking without a recipe, hoping the result is eatable.
The Guy from OZ