I think I'm missing something here. You want 100s of pages accessible from a vertical list, but are happy to wait for them to reload when you re-open one... aren't you just looking for a bookmarks list?
I also keep plenty of tabs open for things that I'm monitoring or want to get back to but appreciate that browser constraints force me to go through the tab backlog and either deal with the tab now or save it as a bookmark for later.
In any case, he could use Sleipnir 6. It's got your hundreds of tabs open market cornered.
Also, bookmarks aren't quite as ephemeral as tabs, so there are different workflow implications.