Try to get Serif onboard
There is a lot of talk on the Serif Forums (forums.serif.com) looking for CMSs to work with Serif WebPlus. PageLime is the current one being talked about.
The only problem with PageLime is that when you republish the site, any pagelime edits have to be redone (WebPlus overwrites the changes). Talk to Serif and if you can come up with a good solution together, a lot of Serif customers are likely to come your way...
This could work with our FTP-XML feature. RapidWeaver users already have support for this, so we’d just have to connect with the Serif folks to get this integrated.
Dale Lewis commented
Some of my customers have requested access to update certain areas of their websites themselves. Simple additions and deletions are what they're after, nothing extra difficult. I don't mind managing updates but if they get too active I have to charge and this would be a perfect way to make my customers happy. If there's any chance Serif......???
I'd talk to them quickly because Surreal CMS are also looking interested (according to the forums.serif.com) ;)