wait, so Astral Chain was initially Platinum's IP initially... I wonder how it changed hands, outright purchase?
I'm more concerned as to what the limitations on them are about... if Nintendo is effectively putting a limit on what can be said, it can only heavily imply they have some kind of plan for it. that being said, if their track record with community plans are of any indication, I'm just as doubtful they're going to do anything with it... outside of potentially being possessive.
as for how it would translate as a Smash combatant... hmm, that's certainly a fun thing to speculate on, I'd likely claim that they'll probably be identified as "Officer Howard" (for those unaware, the player's surname remains the same, the unchosen gender is the younger sibling Akira Howard) or Legionis (the designation of a Neuron Officer with a Legion). they would definitely be designated as a puppet fighter, something along the lines of a desynced Ice Climbers. with substantially more control over the secondary character than, say Luma.
while Officer Howard is capable of fighting on their own (with a baton, a blaster, and a two handed weapon), the moveset really shines when the Legion is summoned. if past history is of any indication with other fighters with multiple weapon options (Byleth, Bayonetta, Dark Pit), it's likely that the starting Sword Legion will take point for the bulk of their moveset... if the other Legions make any appearance, chances are, they only appear for one strike. I'd also say that Unlike Arsene with Joker (since Sakurai's team probably thinks Persona 4 Arena has no business being referenced), the Legion can be attacked, and it'll be encouraged to do so since that's half the fighting force out of commission for a bit.