Oh yes, i thought I answered this, or rather I meant to on Friday and go sidetracked. No more excuses....
So I looked it over and this is not necessarily a bad idea, it's just complex. It would be difficult to explain to a new player that different caliber guns have different visibility detection times and that's why a ship is able to still open-sea invisibly fire at them. This ultimately also still promotes invisible firing to some extent, which is what is not desired.
Sorry, don't follow that
Pre 6.3 the explanation was "when a ship fires its guns its detect-ability increases by an amount that varies with its gun caliber and, if now spotted, this effect lasts for X seconds"
the suggestion was this change to "when a ship fires its guns its detect-ability becomes the same as its max fire range and, if now spotted, this effect lasts for a duration that varies with its gun caliber"
If people can understand the 1st sentence, I expect they can understand the 2nd
Quite explicitly they can't invisi-fire at them any more (the firer can be seen and targeted). The question is simply for how long.
It is wargaming's prerogative and responsibility to make design decisions about the game, and if you want to do it this way that is up to you of course. But I do suggest you have another think about this