Without the use of radar, having a recon-type aircraft (like a PBY, for argument's sake) maintain a visual on a CV should/could trigger it on the country map....the essence being that the CV's position is being reported as it is shadowed. To get the CV off the radar, you need to kill the offending snooper. The balance would be trying to maintain a visual while staying out of the ack, maybe make the difference only a kilometer or two. Pilots would then have to 'work'.
You could actually offer perks for the duration of time a target is maintained on radar. These perks would allow you to purchase faster, higher-flying recon aircraft. The 234 as a recon bird (with position reporting) would be an example.
The downside (I'm sure dozens of us will find other reasons), is that for now, CV spotting is the only real purpose we'd have for a recon option in the game. Is that enough of a reason to implement it? Probably not. Running a recon mission and finding an NOE raid probably won't be an overly popular task.
Maybe we look at what else would make this viable - other convoys perhaps, floating strats running between ports, something like that....I dunno, just thinking out loud with my crayons.
J