This actually involves the critical question how one would see this game.
My characterization of this game (the ideal setting of this game) is that it should get tougher every month so you really have to do anything to send decent agents to Cydonia before you lose the game. But as you have said, this game does the exact opposite since while agents become incredibly more powerful each month, the power of aliens remain relatively constant.
The biggest threat in my opinion is the period where ethereals start to come out, and that wihout psionic LOS mod: it's because psionic attack is based on probability, so no matter what you do you have some chance that one of your soldier will do something that you probably don't like
. And if the Cydonia mission were so hard that you really cannot win the mission with just only rookies, the loss of experienced soldiers at the ethereal missions would have been the real threat to many commandors.
Well, anyway here are some thoughts of mine:
(1) Turn on the aggressive retaliation mission mod: I haven't used this one before though. You can loot a lot from the mission so I'm a bit doubtful that this would make the game more challenging. But what can I say is that the chance that you'll lose your newly built base would be quite high (if the alien ship goes into a base with no soldier, then the base is just lost
). Maybe this is just too stressful? I don't know... Anyone have tried this?
(2) Change the ruleset to your taste: 100% accuracy for aliens, increased hit points etc
(3) Find or Make a mod that makes the game harder as you progress: This can also be done by slightly modifying the ruleset. For example, make aliens that come late much stronger (sectoid, floater -> snakesman -> muton -> ethereal: am I right?). There is also a mod that changes the order of sectopods and cyberdisks (of course, sectopods got nerfed).
I doubt if there is a mod to control the frequencies of UFOs, but if there is, you can use it to make it really hard to get a positive score in late months (so many UFOs so some of them will accomplish their missions, thus getting points). I also think Russia cannot be infiltrated, but if there is a mod that even Russia can be infiltrated by aliens and forcing you to lose when you lose every country by aliens, I think it would be also a great option
By the way, how can I disable the guided shooting of blaster launcher? I also think that's too much so want to know how to disable it