[dogscoff]

For example, a player changes the settings on say DUC I to be as strong as WMG III for one game turn and obliterates a vastely supior fleet.

I don't think this would be possible. If you think about it the plr files only need to contain designs, political Messages and orders. Everything else can be stored and processed on the host.

Therefore, the best you could do with a hacked plr file (I'm guessing) would be to create an impossible design (ie an escort with 12 DUCs & 15 engines) which would be pretty easy for your opponents to spot in-game. Furthermore, there may be checking on the host's side to weed out this kind of irregularity anyway.

Of course I'm probably wrong.