Some one more familiar with the terrain editor will be able to confirm this.
AFAIK radar objects are allocated to fields (which can be captured). Strat objects are allocated to countries.
Of old, fields could have multiple radar objects so terrains could be designed where by a local non capturable field had an additional radar object sited local to the strat.
However this would cause some anomalies
1) There are (or used to be) problems when stuff starts getting too remote from the origin field.... the terrain would become unstable.
2) The field status report for radar would show it still enabled if any of the radar towers were still up.
3) If a (2nd) radar was used that was owned by a capturable field then there would be a possibility that the radar could be "captured" and so confuse players as to its ownership.
The simple answer would be to place an uncapturable vehicle field (without any off field spawns) immediately adjacent to the strat. This would mean that its supplies would have to be disabled for any longer term effect upon strat attrition.
Requiring not a lot more work from HTC would be to enable radar as country owned much as auto gguns obviously are (strats have gguns) and add them to the standard strats.
Or enable radar fields..... simply small fields without hangers or spawns that have a tower, a map room, a radar mast and some gguns..... but when you start looking at small capturable assets you begin to add so much more to the game play.....
Radar fields
Bridge defences
Depots
Artillery positions
Look out posts (Hill tops)
etc etc
