The main problem that I have with the version of stealth being proposed is the dramatic change to play balance it would cause. If I understand it correctly, even with bumping all stealth by one point, dropping a Sharlin's stealth by two would eliminate all stealth modifiers from the shot. Under the current rules, the Sharlin would still have 3+ stealth. Your rule would cause the Sharlin to suck up 50% more fire if it's stealth is reduced in this way. Even the suggestion of lowering the hull value of ships wouldn't really help since it would then be dramatically more vulnerable to anything that ignores stealth.
I think before this would work you would have to work out this issue.
This is why I suggested a "stealth dodge". Rolling more dice makes the results more average across the game and it isn't all or nothing. Unfortunately, I thought at the time that it was too much like dodge. I agree that stealth should "feel" different.
ShopKeepJon