A sensor ship on turn one is most probably the best strategy to grow your civilization exponentielly fatser than the AI.
Let's say you play the Terrans... you rush the sensor ship in turn one (2000 CR) and head for the closest good planet with your colony ship on turn two and rush the cheapest possible colony ship to colonize Mars.
You spam factories on mars and rush a few labs on earth.
You Research interstellar travel, Xeno Economics and the one that give you +4 flat approval. After this you can stop researcg for a while, you have all you need for early colonization spamming.
First colony outside Sol system is formed on turn three or four and you now take the Pragmatic route and gain three constructors and upgrade them to colonizers and on turn five to ten you will have six good planets. You now turn Erath and Mars into producing colonyships which the build in one or two turns by this time at turn 10. By turn 30 you can potentially have up to 20 or more colonies, depending on how many worlds there are around you to colonize.
You will be so far ahead economically from any AI they will never catch up, that is just the way that it is...
This is on an insane map... so yes... this is completely unbalanced and unfun... see no point in playing if I already won the game by turn 30 and the rest of the game are just mopping up the map.
I obviously never exploit these mechanics and I see no reason for them to be in the game at all, they are not a choice, they are an "I win button" which you might as well have for players who want to win the game on turn one... sure... you can use the console to do that if you wish.
I see the point in insane maps being really large but even if you introduce a diminishing return on sensor stacking you will still be able to build ships with good sensor, just not silly good. So that is not really a good argument for using such mechanics.
** EDIT **
Oh... I also forgot to add that by revealing that much of the map will make your Survey ship that much more valuable and both the income and research bonus from that are going to leave the AI even further behind...