Few things:
You can drop the "second post" and the quotes from the SP. It should just contain the design and nothing else.
Meka Ejection: I think the first line should just be "You may draft one large Unique Hero that also has the identity of Hana Song to be her [Mech]." No need for the pilot bit or even the name honestly just incase Hana gets another mech at some point. Change the Mech term there to whatever and you can reference it in the other powers and probably clean up the wording more. This pilot could work with both. Then it should be like: While D.Va is not on the battlefield and not destroyed, if another figure you control with the identity of Hana Song is destroyed, immediately place this figure on any empty space within 3 spaces of the space previously occupied by that figure.
Call Meka: Not sure what the first line is doing, but by default you don't take turns with figures that are not on the battlefield. I think it might be cleaner just to add OM save to the first power and it would probably make more sense.
We don't use Whilst on cards
Not sure why you would suddenly remove all wound markers from this card when switching, I worry that will make her a bit too strong. I'd word it more like so: "Before taking a turn with D.Va, if there are 3 MEKA Markers on this card, you may remove all wound markers from the Army Card of your other figure with the identity of Hana Song and all MEKA Markers from this card and switch the two figures."
Nerf This: Not sure it needs to require clear sight on the power since it's a large explosion, but it's also a powerful effect to get to do something like that for free when destroyed. I struggle to see why you would ever give up her attack for it. I'd probably just let the power trigger after an opponent takes a turn or maybe even moves a figure. Cause you can totally wait for an opponent to charge you in the game before using Nerf This and I think D.Va should always have to choose to use it. It's not something that happens whenever she gets KOed.
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Anyways that's my ramble, my wording is still not perfect yet since things are in flux I don't wanna work on that too much, but hopefully this gives you some ideas to streamline.