Hmm, have to check with The_J how is it done to add extra buttons
But one problem I can forsee is, the "Recon" mission button may be lost after upgrade, Scout to Explorer, galleon to transport
Next problem, the hills and forests will still apply.
Because, the code I use for this current one is literally, perform the Plane Recon mission.
Initially, what I did was create a plane(fighter, bomber etc) on the spot, perform the recon mission and delete the plane.
The area open up just that fog of war applies.
So I did some tests and realise, even in vanilla BTS, after you did a recon mission, if you delete the plane, you lose the vision.
So now, currently it is the unit itself that is doing the "Plane Recon" mission, except if it is done by land units, vision is blocked by forests and hills.
If it is done by naval units, vision is still blocked by forests and hills, but whatever, naval units should be scouting the ocean anyway.
Thus, even if I manage to add the recon mission to the unit, it will still suffer from hills and forests, because currently that is what the unit is already doing.
For stationary ones, that is possible, except require tedious turn checks.
1) Every turn, loop through every single unit of each player.
2) If it has recon promotion, do recon.
As for longer they stay more area, not possible via python.
Some of them may be done better in SDK