Hi everyone,
I'm new to the forums and this is my first post. I haven't yet played Arkham Horror so this is my first foray into the Lovecraft mythos, but it has really got me excited, to the point that I'll be buying AH soon. I a realy digging the theme of ES so far and have a few ideas to add to the flavor (read difficulty) of the game; let me know what you think...

At midnight if any adventure has an active monster, that monster must move to an adjacent adventure card (the active players choice) and a new monster is chosen from the cup to replace it.
The idea being monsters don't like being hungry/bored/lonely and will start lurking about for food/food/food. The reason it's replaced is that particular adventure has been affected by an AOO and monsters will spill forth from the void until the investigators can complete it (and close that gateway). I realize that there are some "monsters" that don't fit in this thematic variation (like the cultist), but who says they're human cultists, right? This would encourage players from ignoring adventures that are more challenging in favor of going for the easier ones (always dig up the baobab); after a few game-days the museum could be over-run with monsters...

When it comes to the Mythos cards... remove all the cards that state no lingering effects for the day, as the AOO is nearing wakefulness and has a greater effect on reality.

Lastly, once the AOO has been locked away or defeated the rules state that all investigators win (HOORAY!), that's it, game over, have a good night everyone, but it got me thinking; there is still a (now un-cursed) museum with horrors lurking in the shadows for the Smith family, when they arrive on vacation from Tulsa, in the morning. It seems pretty callous for the investigators to abandon the job half done... "Yup, we kept Azathoth from blasting the world to cinders, but the bloated woman in the storage closet? Hey, that's on you, I need to feed my cat."
To tidy up the loose ends, the remaining adventure cards in play at the time the AOO awoke (and was defeated) or locked away (not the ones in the deck, good god!) must be completed. The only variations to the rules would be: no more Mythos cards are drawn at midnight. Any doom tokens, or Other World cards that are rewards will generate a monster instead of being added to the doom counter or adding an Other World card for play, and each ES awarded would count as one trophy. Just because you've saved the world doesn't mean you won't get hit by a car on the way home... Once the museum has been cleared, players who survive count their trophies, the player with the most, wins, and buys everyone a round as the sun rises... I realize this goes against the “co-op” setting but I like it…
I appreciate everyone's feedback...