An idea occurred to me after I posted in the new maps thread. Currently it is possible to create either land or sea spawn points in the terrain editor, but their size is fixed. I believe it may be possible to alter them globally as an arena setting, but this is not usually practical since it would create bugs in the terrain (SPs crossing coastlines etc.)
My wish is to have a slider in the TE that lets the terrain builder alter the area of each individual spawn point over a given range, up to say twice the current standard area. Failing that, maybe a couple of global settings, one for all the land and one for all the sea SPs in a terrain.