Bad Design Alert: Don't create a problem just so you can solve it

Advice: If the premise of an ability is your interpretation of how the rules should work rather than what is actually written in the rules, you're going to be in trouble.

Examples: You're designing a weapon special ability or spell that makes firearms as quiet as bows. Two-handed firearms become as quiet as longbows, while one-handed firearms become as quiet as short bows. Congratulations, you just designed an ability that (from a RAW perspective) does absolutely nothing. Don't get me wrong, I also think firearms should be louder than bows, but since the rules don't support this interpretation, I just house-rule it in my games. (I think it may have been mentioned in flavor text that guns are loud, but nothing in the rules text suggests they are louder than other weapons.)

Another example would be an ability that makes your teleportation spells look like the target(s) turned invisible instead. Or the other way around, when you turn invisible, it looks like you teleported. The problem is that the most iconic teleportation spells, dimension door and teleport, don't describe how you vanish. Does it look like using a transporter in Star Trek? We don't know!

The only teleportation ability (that I remember) that involves a visual description of the effect is the cape of the mountebank which explicitly describes the visuals: "When he disappears, he leaves behind a cloud of harmless gray smoke, appearing in a similar fashion at his destination." If the dimension door spell had the same visuals, it wouldn't make sense to repeat that in the magic item description, so it is safe to assume the spell doesn't have any similar visuals.

Designing an ability like that forces the players to interpret a rules element in a way that is not supported by the rules. Don't do that.

Even though it might seem like you've only created an ability that does nothing (which are annoying but harmless), you may actually also start a huge rules debate, lots of FAQ requests, and whatnot. You've created a precedent that will plague RAW discussions forever. Suddenly, retroactively, you changed how the game works. (Kind of.)

So. Don't. Do. That.

Design stuff that interacts with existing rules as written.