We have (had?) a potential government customer that has a strict set of rules for their machines. MySQL Server cannot be installed on the same server as the application that uses it. They want to install Nagios XI but they simply cannot allow MySQL to be installed on the box, even if it's going to be offloaded to a separate server later. Simply put - if Nagios XI has to install MySQL, then they will not purchase Nagios XI. So at this time, we're at an impasse with regards to selling them Nagios XI.
I think it's time to allow the install process to name an external MySQL source. This is not 2009 anymore and there are a LOT of organizations that run well-tuned highly available MySQL clusters that Nagios XI could install to from ./fullinstall rather than having to move to once the install process is over. This would also set the stage for Nagios XI containerization within Docker or other entities where the application is separate from the database (and possibly from the web server as well, but that's a battle for another day).
Please consider this a request to add the ability to specify an external MySQL server during install, removing the forced need to install MySQL on the Nagios XI server.