Feat: Misty Step as a bonus action (once per turn) [equivalentish to dash as a bonus action]. Sneak attack after Misty Step does extra 1d6 damage.
Yeah that could work. I'd like it to be in some way different from how others teleport, but a feat won't do that, even if you drop the sneak attack boost, so as a feat that is a good job of it.
I might change the sneak attack boost to a compatible benefit that doesn't assume you're a rogue. Like the bugbear ambush ability.
Maybe, a number of times equal to your PB you can deal an extra 1d8 damage after you teleport, as long as you [same requirements as sneak attack].
you don't ask D&D not to offer you a modest selection of pre-made classes that package a handful of special features balanced around limited uses.
You sound ridiculous. DnD does this without anyone needing to "ask". All kinds of character options take otherwise limited actions and make them at will, or take minor at will actions and make them more powerful. Some even do both.
It's literally a major part of the design of character options in dnd.
Also, 5e is the oddball in the last 3 decades of dnd for having a "modest" selection of classes, rather than a couple dozen or more.
My actual ask, as opposed to your insipid mischaracterization of it, is super common. That is, a 3pp or homebrew class or subclass that focuses entirely or primarily on something that already exists in the game but doesn't have a subclass or class dedicated to it, leading to a less limited form of the thing than can be reasonably achieved in options in which it is only part of the point of the option.
That is...literally one of the most common ways that classes or subclasses are built.