Instead of a single spawn point per field how about a dozen or so?
The map shows an arrow pointing to a marked area, within which are a dozen or so spawn points. The FE sends you to one of these spawn points on a random basis. Map designers could choose to have sps ringing a field, or all to one side.
This screws the spawn campers, since they have only a one in twelve chance of picking the right sp. Instead of camping the sps, they are forced to set up ambushes closer to the field. Aircraft also have a harder task finding gvs.