Domain Access instead of Multisite?

Domain Access instead of Multi Site? Other Ideas?

We are using multisite Drupal currently for 3 sites. Lets call them:

www.mysite.edu (main site)
support.mysite.edu
students.mysite.edu

We have a number of issues with multisite. We are looking to add a couple more sites.. which will compound these issues.

1. Three different sets of configurations (Drupal config options set up through the admin interface)
   a. While some things are shared, such as theme and module directories. We still have to do configuration changes in 3 different sites admin interfaces. Example: We decide to make a tweak to how the WYSIWYG editor is working.. We have to do this 3 times.
2. Module updates SHOULD be a breeze between the 3 sites, but because the sub-sites use a couple of modules the main site does not, logging in to them separately (or blindly trusting drush..) to update modules is still needed. Testing the module changes on all three sites is also required.
3. The same administrators run all three sites, and some of our editor provided content requires approval to be published, so We have to log in three different places to approve content.
4. We are having an issue where, as all three sites are on the same server. We will sometimes be logged in to the main site, and then when going to a subsite, we will get a nasty browser error.. timeout or something. I believe it has something to do with a conflict where the different sites do not know how to handle us being logged in to one or all simultaneously.
5. OTHER ISSUES

One more potential wrinkle:
1. We are using ‘Secure Pages’ module to redirect important pages to https (pages such as: node/add*, node//edit, user, user/, admin, admin/* … since this has a base url set, it could disrupt the plan to make the new URL’s persist for the visitor. On the other hand, all these pages are for admins/editors, so it is less important that the URL persist in their browser.

Due to this we are looking for a way to make Our SINGLE drupal site ‘contain’ the sub-sites within itself. Domain Access APPEARS to be the only module to help with this. But it COULD be something you can do with Apache config mostly, If I knew how to do that.

Requirements:

1. www.mysite.edu (main site) works as usual
2. support.mysite.edu URL goes to ‘unique’ homepage with its own menus. If the site visitor enters the site from the support.mysite.edu URL, the name should PERSIST in their browser bar, NOT switch to something like www.mysite.edu/support.
   a. We attempted to make the domain name support.mysite.edu point to www.mysite.edu/support. No luck with that approach so far. The goal there was to make it so that any subdirectory/subpage in the support area (mysite.edu/support/*) would keep the support.mysite.edu URL)
   b. Seems we MAY have an issue with pathnames in the theme if we bury things one subdirectory deeper as desired in a. above.
3. Same as 2. Above for students.mysite.edu.
4. Persistence is key.. if you go to support.mysite.edu, your URL bar should always say support.mysite.edu /SOMETHING, not switch to www.mysite.edu/SOMETHING
5. We may add 2-3 more sites, but I cannot imagine it ever going over 10 while still on Drupal 6

Use case.

• A user wants to go to our main site.. the type www.mysite.edu .. then they navigate around and their URL stays www.mysite.edu/WHATEVER while they on the site (unless the below conditions..)
• The user visit support.mysite.edu, the URL in their browser STAYS support.mysite.edu for all subpages of the support area.

Is this possible?
Picture Attached to lessen confusion from my explanation...

Thanks!
Jeff