I’d stay away from settings. Everyone has their own take on them and they are all over the place on opinions.
I see nothing wrong with the graphics currently presented.
It's as much about retaining existing players as it is about getting new ones.
There are several settings that could be tweaked, and several maps removed. You're right in that there are varying opinions, but there are a few commonalities that many agree on, night time being one, sideswitching timer being another, as well as the removal of certain maps.
For example:
nightlenghthhours = lessen or remove totally, currently set at .3 of some variable (hour?) = 18 mins approximately
Observerseen, planeseen, and vehicleradar, vehicleseen, and vehicle sector = icon/radar ranges
changecountrytime = side switching timer, currently 21600 seconds (6 hrs)
daystilterrainchange = currently at 1 week, could be lowered to 3-4 days
There are a ton of viewable settings, and some that we do not have access to (eny tables), but all require changes that only HTC can make on the server side.