New ability for ‘stealth’ and/or ‘view stealth’ units.
This skill is rarely used because it does not have many practical applications. So I propose that these types of units can see the technologies that you are investigating, the units that you are creating and the destiny of the metropolis. It would also be good if you could see the shipments that are in progress from the metropolis in case you are near the destination of the metropolis.
The unit must have both abilities (‘stealth’ + ‘view stealth’) to be able to perform this level of espionage.
Hot air balloons could be the exception and so could Dutch emissaries. That is, they do not need to be stealthy to have this intelligence ability.
Above I proposed a more practical way to implement the ‘spy’ and ‘metropolis blockade’ upgrade.
I propose the same for the spy upgrade, but this time for a single player at a time as I proposed with blocking, not spy on all opponents at the same time, as it would be very expensive.
For hot air balloons you do not need two politicians (one that provides a temporary balloon, and the other indefinite ‘advanced balloon’). Just in case the player opts for the hot air balloon at age 1, enable an upgrade on the church for age IV that will make the balloon last longer, and the explorer skill recharges faster.