I am for diminishing returns one way or another. That way sensor technology doesn't lose it's meaning (with 15 max you would have 15 right at the start).
In addition it should make everyone happy (except those who scream "freedom!" for the sake of it). It supports early game exploration, doesn't make scouts obsolete, and it supports late game or huge galaxies when big sensor ranges are necessary. In addition it still gives you the choice to build a cargo ship full with sensors as "sensor ship" - it just won't be as effective.
It's sad to see that the developers took the easy way and kept the game unbalanced.
However, the game is supposed to have a 7 year lifecycle. And I am pretty sure, that they will get balanced sooner or later. Maybe with a patch in some months. Maybe with an expansion in four years. The more players become experienced with the game, the more players will realize the balance flaw. People who are not aware of it, will not complain about it. But the more experienced players become, and the more people feel pushed to play this way, the more stress will be on the developers to fix it.
So if you want to do anything about it, it might be best to watch youtube videos / twitch streams about the game and help the guys playing by making them aware of this superior tactic if they don't already use it.