The gotchas you'll face are Ubuntu 16.04 uses PHP7, which isn't supported by Xibo currently, so you'll need to downgrade to PHP 5.6, and get a working zmq module from somewhere for that.
Secondly, Apache uses the .htaccess file to define the URL rewriting rules that make the CMS work. If you use nginx, you'll need to roll those in to your nginx configuration as nginx won't pick them up from the .htaccess file.
You'll only need to create the
web container. The
xmr containers don't use Apache so there's no need to create new variants of that.
If you do go this route, and later need support, please can you be clear that it's your own docker container as otherwise we'll assume they're the official project ones - and since the environment in yours will be very different, we won't know.
What I would say is that yes, I tend to prefer nginx too, but since almost every call to the CMS requires a PHP process to handle it, there's far less of an overhead in running Apache with PHP built in to the web engine than there would be for a normal site where alot of the content is static/non-generated files, and only a small amount is PHP based. You may therefore find that the effort involved in building and maintaining your own distribution is of limited performance value.