Even if you are not using Thermal Vent necessarily, if you place that or any other fixed weapon in the hardpoint opposite the missile, it becomes quite easy to switch cockpit mode and use its sight as the opposite corner of an imaginary triangle. Skip a bit through this video to see it; this was from much earlier when patrols were unable to attack Commanders flying close enough to the Titan, so the same rescue method will work no longer, but it should demonstrate the aiming a lot!
One of my goals while recording that was not to miss a single missile.
Stockpiling at all will be a bit of a risk; the time between Titans is going to increase merely due to Spire sites not providing enough peripheral progress to reach the Titan, let alone those with close-to-200 systems. To an extent that means more time to stockpile rescues, but mind that Frontier also has more time to change things!
Setting all of that aside, I suppose a good answer could be to compare the number of Counterstrikes with the number of Control systems evicted, and shift rescue activities away when other efforts¹ surpass that number. For example, if we can clear ~20 systems then it should be as well to help with rescues if there are at least ~19 Counterstrikes, otherwise stockpile elsewhere if there are fewer.
1. While not distracted by a quite important Community Goal, of course!