I do wonder how often people check their opponent's damage deck for accuracy. It may be easy enough to count cards but is some circles I could see "cheaters" trading out cards very harmful against their squad for ones that aren't so detrimental. How many swarms care if they get hit by the critical that forces the ship to "discard a secondary weapon" when they never carry any?

That card can be go good/bad depending on who takes it, it's always a fun one!

It's fairly obvious though when the opponent draws 3 of a card and there are only 2 in the deck.

It may become "obvious" that a damage deck has been tampered with if you see three, or god forbid four, of the same card but that means having a good memory or being observant enough to notice it happen.

Typically in my group, we are using my ships and gear. I have each deck from 3 core sets, sleeved, and in their own small zip loc bag.. no fuss no muss, I keep them separate for convenience. I have a 4th core set (unopened) and may mix 2 just for grins and ease of play..