This project will require a creative approach.
We are selling multisites from Joomla.
Our subsites are not subdomains, but subdirectories (mod_rewrite).
So it is [url removed, login to view] to get to username's site.
Sites obfuscate the database from each other, but use the same set of files.
Right now we are selecting a set of DB tables by prefix. This is horrible because it creates hundreds of tables with just a few clients, and makes upgrading a nightmare.
We want to run this solution using only a single set of tables, but still allowing customization per site.
Not all, but most, tables need to have a site_id column added, and somehow all the queries against this table throughout the system need to add a WHERE or otherwise respect site_id.
(If you have an idea that requires all tables to be affected, this is fine, as long as it works as described.)
We are open to other ideas, as long as our end goal is met: we want to run a single set of files, single set of tables, but allow unique content between "sites".
Please say something about how you plan to approach this project, so that we know you understand the requirements. You can say this in private message if you do not wish to share such a valuable secret publicly. If you do not offer some indication as to how it will work, we will assume you have not understood this description.
I do look forward to forming a long term relationship with the party that can get this done, as it will be a display of professional level capabilities.