Oh Ebay,
Being a pain in the ass since 2009. I had to do something of a CMS for a project and actually did manage to finagle javascript into it, but it wasn't pretty.
Anyway, two questions:
You mentioned server-side, as well as you should have, do you have the host/site yourself already? If so what/who (AWS, fatcow, dreamhost)?
When you say you want to make it easy to make adjustments, do you mean to say the data in the FLA file/source files should be arranged such that you can change them easily yourself OR do you need a management system independent of the source files (i.e: you don't want to touch the code/source). The latter would take a bit more time, hence the question.
Regards,
-Andy