There is a database with content, a place to manage the content and then a window to view that content. So we have three things that need to be addressed.
It sounds like your head office already has the database in place.
2. Content Management
How does the content currently get into the database? There must be some form of editor/CMS or do the developers manually add that?
3. View Content
They are proposing to use HTML and some server-side language to display the content. While this will get the job done, you correctly pointed out that a CMS usually provides additional functionality other than just content management. It provides a user-interface for content presentation, SEO, search, caching, multimedia uploading, social media integration, etc, so there are definitely many, many benefits. I don't think your head office would take the time to emulate all those features, so a CMS would be in the best interest.
To address the database perspective, it's perfectly feasible to build a plugin that retrieves the data from the original database and store it in the CMS' database. This could be securely setup and you'd get their database content, plus all the additional functionality a CMS provides.
I've recently started in a marketing role at a new business and am in discussions with our head office to get a new website built for our retail business.
I have requested that the new site has a fully editable CMS (I've used EpiServer and Joomla in the past), however the head developer at Head Office has said he want's to build the new site in HTML without a CMS and load content direct from a database.
Instinctively, I'm fairly certain this is the wrong choice from a design and SEO point of view but I'm not sure of the benefits of a HTML site vs CMS aside from the editability point of view.
Does anybody have any thoughts on how a site should be built or the advantages of a HTML based site over CMS?