Hi,
1/ first of all, the aliens DO NOT see your troops after 20 turns. That's simply not true and never was.
When the cheating is activated, the following happens:
- the passive aliens (e.g. leaders inside of the UFO) become active and will be forced to scout, i.e. eventually come out of the UFO... but they do this BLINDLY and RANDOMLY
- all aliens will prefer combat if possible... they will not try to escape or to set up ambushes so much
- your units will be marked as "previously spotted"... which is DIFFERENT than being visible... aliens will use this information for some minor calculations, but almost all of them are just cosmetic and you will never notice any real difference... with two exceptions:
- the first exception is Psi attacks, because they can be performed without actually seeing your units... if you want to turn this off, there is a standard mod called "UFOextender_Psionic_Line_Of_Fire", which will require that the alien must also see your units to perform the attack
- the second exception is Blaster Launcher
2/ secondly, your example with the Chryssalid is completely false... and also the best counter-example:
a/ the last Chryssalid would cheat already after turn 10... when there are 2 or less aliens remaining, the cheat turn is halved (20 / 2 = 10). So if the Chryssalid could cheat (and let me repeat that they cannot!), then it would start hunting you much sooner
b/ majority if not all Chryssalids don't spawn as passive aliens, so the cheat turn doesn't make them much more active than they already are... unless they are stuck somewhere by accident
c/ since Chryssalids have only a melee weapon, they NEVER set up ambushes; also they almost never try to escape (btw. escape is considered only when they are seen, so irrelevant for our case)... so again the cheat turn doesn't make them change this behavior either
d/ lastly, the Chryssalids don't have a psi weapon or a blaster launcher, so they can't cheat with that either
Bottomline: the Chryssalids behave 99% the same before the cheat turn and after the cheat turn
3/ If I still didn't convince you that changing the cheat turn won't help you... you can change it in the alienDeployment.rul, but you must do it for each deployment separately. It's not a global setting, but an attribute of a deployment. Example of changing the cheat turn for the terror mission deployment and supply ship deployment:
alienDeployments:
...
- type: STR_TERROR_MISSION
cheatTurn: 999
...
- type: STR_SUPPLY_SHIP
cheatTurn: 999
...