Can they make homing canon shots? So they just need it going in the right direction.

Due to ships able to rise and fall so much, canon would difficult to aim. If they develop gun turrets able to be adjusted, those could be set up.

That would suggest that these other worlds are beyond the outer gates, as I doubt humans can survive long term in the never never.
 We know the attacks on the gates vary, could the humans that established those world got there during down times.

I thinks cops is Cosmere auto corrected somehow.

I wonder why power core crystals are the only ones to increase in strength due to age/use, since all crystals are apparently vat grown. It could be possible.

 So there are two explenation for lost power cores, they either were brokers so exploded or they were lost and fell to earth. Due to them gaining in strength as they age, I wonder if a ship can detect them on the ground.

Harry and Tavi are said to be part of the same bloodline, not necessarily descended from the same person. That heritage bestows something important. Like how Constantine had a heritage that allowed him to face epic level magical threats.

It is not the cops are but local multiversal region, I would say it would be akin to the else where's of the dc multiverse. But instead of based on the same world, the else where's are are different what ifs while these are entirely new worlds.

Harry has said the never never potentially allows access to alien worlds, so those different worlds could potentially be in the same universe. Nothing we have seen has definitely made it know that these are differing worlds, just that these humans are no longer on earth, and their magics have gone another path.

I wonder if the builders created the original version of the vatteries?

I wonder why power crystals are the only one that gain in strength over time and use. Imagine if the other crystal can be grown so they mimic power crystals in this form. It would allow large scale implementation of high level crystal engineering. So not just used for the military or the nobility.

Nobility often intermingled with warrior families. Their ancestors rewarded for their actions in battle. But I would think they would be eager to marry daughters to warriors, to bolster their influence and power.
 I can see them making advantageous marriages in the cadet lines, so even if the high nobility disdain them, the lower ones would be eager to accept them.