Issue:
Is "Maximum Land Level" the new "Maximum Elevation Level"?

Ive tried adjusting this in /profiles/ but it doesnt seem to spawn any more inland by hightening the value.
It is currently at 200 and it still spawns only close to water/beach.

Idea: 
To allow decay to be the despawning model of a base. For instance, i use the bases as "fillers" for a low pop server. And, it would be nice to allow the bases to decay at normal rate instead of swiftly vanishing when timer runs out.

yes. that is not what it's used for though. it determines the surrounding height of the terrain and allows bases to spawn based on that. if you set it to 200 then bases can float 200 meters off the ground. you should not modify it from its default for this very reason. the maximum setting is 3.0 so you can't accidentally set it to 200 which would break the plugin.

by default all bases will spawn everywhere on the map and if this isn't the case then it's your map. Grids To Block Spawns At, Block Spawns At Positions and Zone Manager plugin will block spawn points.

      "Allow Raid Bases Inland": true,
      "Allow Raid Bases On Beaches": true,
      "Allow Raid Bases On Ice Sheets": false,
      "Allow Raid Bases On Roads": false,
      "Allow Raid Bases On Rivers": false,
      "Allow Raid Bases On Railroads": true,
      "Allow Raid Bases On Building Topology": true,
      "Allow Raid Bases On Monument Topology": true,​

enabling roads will help with some bad maps. disabling beaches will force the use of more inland spawns, but if your map cannot handle it then it will not work.

your idea will be implemented in the future but it is not possible yet.

I have this one "Allow Raid Bases Inland": true, and i readjusted the maximum land level and will see what happens.

"your idea will be implemented in the future but it is not possible yet." - Wohooo! :)