Just for run, 6/9 movement that ignores any terrains is already enough to run away from a heavy to assault mechs. It is actually faster than some heavier mediums as well, for most 50 to 55 tons mediums are only have 5/8(/5).
It is not expected to be survive against fast mediums and lights anyways, and it is the other friend's duty to cut them down before they can do something to their Yellow Jacket friend. At first, I don't think that most officers are crazy enough to NOT attach any 'escorts'(ironically, it IS the escorts for the most forces actually) to them even if they can. Also, concentrated fire of gauss rifle shots is a serious threat against lights as well.
And, who denies that it is a niche design? It is, and we all know that build the force around it is already a problem on it if we use it heavily.
my point is,instead of being an adjunct that enhances your forces, the Yellowjacket becomes the center of your forces and everyone else becomes the adjunct.
it's really the only way to make it work. It has to be the center of both your using forces, and the forces on the other side have to be pretty specifically designed to be vulnerable to it.
which makes it not a good niche unit, just that it can be adequate in that niche-assuming all factors in the engagement are prearranged to suit it.
as I said before, I can use Ferrets, Cavalry, H8, H10, Pinto, Ripper, and so on as an adjunct to a force, and do well with them as supporting players, it's actually hard to arrange things to make those designs utterly useless. it's EASY to make a yellowjacket useless by comparison.
How? get something on it that can threaten it. and by 'something' I mean virtually any VTOL except a Karnov (which is unarmed in the base model) or other unarmed unit in the same movement class, or any 'mech that can go at or above the same listed speed. even bug-'mechs, or anything armed with an LBX, HAG, or other cluster weapon with range.
my fave for this demonstration is the pathetic little old LRM carrier, but this can be done with SRM carriers too, or (god forbid) light vehicles-because the YJ is a
light vehicle.
other favorites include VTOLs considered borderline useless for other roles, like the Mantis. a Mantis can make providing that fire-support nearly impossible. even going one on two vs a Yellowjacket.
but then, I
tend to be a movement player, and avoid 'stand at medium rolling dice' whenever possible. in a sense, the Yellowjacket is an exercise in showing why going to the top of the weight class with VTOLs isn't necessarily the best idea, or even a good idea outside of a specialist transport model. (and then, only if your intent is to get a one-use APC to move a company of infantry a little bit closer to the front.)