IIRC, the astreus used to be able to enter the air layer, and then move around in the air layer, rather than what it does now, which is briefly enter the air layer to pick things up, but cannot actually move around in it. Would it be possible to revive the old code that allowed it to do that and apply it to a new unit, say a revamped pergerine as an atmospheric/orbital fighter?
If you have a copy of early beta, then they are notoriously terribad about closing old hooks they stop using. Just use the same code they used to, should work.
This was a case of how the engine handled it being changed, not any jsons being change AFAIK. Old code would be the same as current code.