I think that a better draft platform will incentive posters to elaborate on their posts and topics more carefully.
I think preview was already a good tool for us to check if there are wrong on our statements or posts.
Since we barely use the drafts then I think we don't have to issue any development about drafts.
In my opinion, saving 100 drafts is completely unnecessary and deleting them after 7 days defeats the whole purpose of drafts.
7 days is a short period, and people may forget about a draft and lose it. I believe most users simple this draft page because it is too risky to lose your work.
I always post some quality topics in our local board and also posted some of my services that consists of graphic design. Then, I'll try to check on preview if there are errors on my thread. I didn't come up to the point that there are already 100 drafts in my draft section so I think it's really impossible.
If you've thought something good then remember the main idea of that topic then try to post it as soon as possible. You don't need to save it on drafts, all of those ideas will come out by the means of remembering the main idea. I only find the preview tool very useful and if I've got any emergencies during creating some post, drafts are there for you.