When I think of a Butler I think of someone who monitors various aspects of a household/estate, stashes that information and uses it to improve service.
 

Last night I was also thinking about network configuration.  It might be good to know if people are using the database over the network more often than a standalone with BindAddress 127.0.0.1.  It might also be good to know the distribution of NIC speeds (10/100/1000/10000) as it might help when determining where to focus development efforts.  That is, if a ton of people are using 10Mbps (unlikely) maybe it might be useful to look at improving compression or other data related parts?

I imagine the MariaDB version will determine what libraries people have installed because of various dependencies, but it might be useful to collect that information as well or whether they're running custom C libraries versus stock and etc because this might point out areas with problems for high-end users.  I'm not familiar enough with the code base to know which ones MariaDB might want to monitor, I just thought it might be useful to think on it some more...