Even as a new player, I definitely like the cleaner more immersive UI look. However, I do agree that an unsuccessful spot could either mean it's a friendly or an enemy that you're technically not supposed to be able to see.
I think a good compromise would be this: if you attempt to spot a ship and that ship is a friendly, then it will simply flash a team-color X on the ship for 2-3 seconds and then fade out. That way, you know for sure that it's a friendly and not an enemy that's in some technical hiding spot (even though you can clearly see it).