I'd say it would be perfectly legit to release ships with essentially the same stats & costs but different models and new upgrade cards. If well done I'd buy it just for the variety.

Yeah it wouldn't be too hard to vary the stats a bit and as long as the point cost is consistent with the power it becomes a matter of personal preference in fleet building.

If the new SD from FA is maybe heavier shielded and armored but only goes speed 2 it can have a place in the lineup no problem

At first I was thinking FFG didn't have a precedent with throwing a new ship from media in without a competing ship of the opposite faction (consider the recent X-Wing Wave 8, with the Ghost vs the Inquisitor TIE), but then I remembered we had one: Wave 3, HWK-290, released opposite of the TIE Bomber and Lambda shuttle.

So perhaps Finalizer could be released after all?

I wouldn't say so, HWK-290 was released as the first rebel ship with a crew slot opposite the Lambda as the first Imperial ship with a crew slot. Ofc, HWK-290 was pretty sub par while the Lambda at least was fat.

And while HWK was the first EU ship to be released, it was at least the same era, releasing Finalizer without any rebel TFA ship would be akin to just releasing the X-Wing T-70 for X-Wing, but not the TIE/fo.