Figured I'd post what happened here, let others review the house rules we had for this alternate mode, and just share results.
We decided we wanted to play a "Campaign" against a batch of IOs, continuing -some- progress, but we also wanted to make sure there was still some balance to it. A lot of campaign options we'd seen wound up with the investigators power ramping up to the point that the game became trivial.
Essentially, when you finish a single game in "Campaign" mode, you use that same investigator in the next game. The rules for the carry over are as follows.
1. You are only allowed to keep a number of a type of items items equal to the number of those items is your character's starting "kit". IE, if you end the game with Finn, who is allowed 2 random draws, and have Holy Water, Elder Sign, and Enchanted Blade, then at the start of the second game, you can only choose to keep 2 of those 3 items. This applies to Commons, Uniques, Spells, and Skills.
2. You can recover your fixed starting items, and they do not count against the above limit.
3. If your investigator survives a game session of Arkham, they gain an "experience" slot. This slot can be used to keep one extra item outside of your kit. Your experience slots cannot be duplicated to keep the same type of item. IE: Finn has finished two games, and has used his first "experience" slot to keep an extra unique item. The second game, he has to choose a different type of card. Note that -one- Ally can be kept with the experienced slot. (For characters with an ally in their random/fixed kit, this works just like other items.)
4. Conditional "Items": Blessing, Retainer, Bank Loan, and other specific effects granted through a circumstance other than random draw. These are carried over.
5. Madness and Injury cards should be used, to help balance long term gameplay, and they do carry over. An investigator may choose to burn an experience slot from a won game to remove one of these cards.
6. Cards that specify they are removed to the box are removed from the campaign. The exception to this rule are monster tokens. Yes, this means there's a total of 4-5 elder signs for the 8 games. It does also include gate and mythos cards that are removed to the box as well. This means completed rumors do not return.
7. Clue Tokens do not carry over. Money does. If an investigator starts out with less money than their starting kit, they do regain money to match their starting kit.
For our game, we drew 8 ancient ones, randomized them without looking, and flipped one per game. We decided to run a single expansion each game, chosen -before- choosing the AO from the pile. If an investigator retires or is devoured, a new investigator is chosen, and that investigator is removed from play. We then drew three investigators per player, with a player picking one of the three drawn and the other 2 being returned to the stack. We did not set a max number of investigators, so we have the entire cast from Base, Dunwich, Kingsport, and Innsmouth available.
We decided for this run, we'll just restart the current game with new investigators if the players lose, with the losing investigators removed to the box along with devoured and retired ones. This means we'll probably power through the 8 games eventually, due to the sheer amount of investigators, but the body count should be an amusing statistic.
Results: We played four games with this set up, and it was surprisingly balanced. While we won all 4 games, we never really coasted to a victory with ease.
Game 1: Base set with Azathoth. Pretty simple to start with. Players drew Ursula, Zoey, and Skids. Game went fairly smoothly, but then again, our group has pretty much mastered base set with Azathoth during our intital "tutorial" sessions. Won by seal victory. Skids and Zoey ended with a madness each, Ursula came through fairly unscathed. Unfortunately, I failed to keep up with what items were being kept over all. I was playing Ursula, and kept the Bravery Skill for my "Experienced" Slot.
Game 2: Dark Pharaoh set, used the Dark Pharaoh Herald, and Chaugnar Faugn. This game got ugly, quick. The Pharoah made the Anchient Whispers marker fairly useless. Ursula got a pentagram of blood and got cursed for her trouble, but she also had the healing stone to off set the curse effect on the pharaoh. The players fell behind on the monsters due to three back to back midgame surges, and then 3 more gates popped, leaving only one gate before AO awoke. Skids and Ursula -tried- to close gates most of the game, (skids had some insane lore bonuses), and Zooey played monster hunter. Unfortunately, the cup was vicious to the crew. Zooey wound up having Amnesia, Hysteria, Mania, and Depression, and Xenophobia, before finally giving up the fight to retire. Skids got Xenophobia and several Injury cards and ended up retiring as well. Ursula was handed an elder sign by Zooey before retiring, and Zooey's replacement, and drew an elder sign on her starting kit. Skids retired and was swapped for Drake on the last 3 turns, and Drake proceeded to go out, fight a cultist, and lose. (The rumor that bumped cultist toughness was in effect) Drake chose to toss items instead of take an injury. The duo of Marie and Ursula charged a pair of gates, and with a pair of monster surges instead of a gate, the two elder signs were used to seal off the game. This meant we were down 2 elder signs for the campaign as well.
Game 3: At this point, with 2 investigators essentially starting off fresh, the "ramp up" of investigator effectivness was pretty much not present. Ursula was fairly well stacked up however. We ran King in Yellow, with Nyarl as the AO, and using the KIY Herald. This game was.. weird, for our play group. Marie went out and solo'd the Terrible Experiment on turn 4 when it popped up, manhandling the entire spawn. The Black Man then spawned, and she charged it, and proceeded to fail the luck check. With 4 luck to roll, (She had the luck skill) and 5 clue tokens burned. So Marie is devoured, and Finn comes in, in his place. Drake does monster clean up, while Finn tries to get prepared for the fight, and Ursula works on gates. But, the outskirts kept refilling, causing terror level increases. We drew 2 blights at first, the first being Miriam, which hurt Drake greatly, and then the Dean. At that point, we decided to quit pulling blights, and focused on gaining up clue tokens. Nyarl popped due to a mix of doom/yellow sign tokens, and proceeded to get -wrecked- by the team. It was our first time using Nyarl, so we were kind of surprised. (We decided at this point that blights would not carry over)
Game 4: Kingsport set. Ursula, Finn, and Drake are -armed to the teeth- thanks to the carry over of items, and we figured maybe we'd peaked out and would start cleaning up. (Which, would be bad, but we were just playtesting house rules.) AO drawn was Ghatanothoa. We used a herald, Tulzcha. We'd never used Kingsport before, and so we had to take a moment to figure out how rifts worked, game starts, and it's just a mess. Lack of board knowledge -really- hurt us here. Tully had no effect whatsoever beyond his starting effect. Ghata slowed down clue token gain however, and Finn was patrolling Kingsport for the rift situation, and we had 6 gates in 7 turns. Ursula charged a gate with max Move to the dreamlands, and then drew the dreamlands card with the Dhole graveyard requiring a sneak check or be devoured. And so, Ursula was finally gone. Patrice was drawn in her place, but it was too late to salvage things and Ghata awoke. There was some trading during the Refresh phase, so Patrice and Drake were set to do damage, but Finn had been mostly focused on hunting elusive cultists (which never actually seemed to appear) and had a low fight and move check. Patrice and Drake managed to ping away a few doom tokens while Finn moved sliders during his refresh phase, but it took Finn 3 rounds before he managed to scratch the AO. Movement Points ran out for Patrice, on her last turn before getting devoured, she passed her weapons over to Finn, and Drake was devoured the following turn. Finn had an ace up his sleeve for Ghata though, which was his motorcycle. It took him a few turns, but Finn managed to finish off Ghata thanks to the initial team effort.
However, this does put us at game five, with Finn being the only campaign survivor so far.
Our house rules seem fairly balanced so far, surprisingly, and we're looking forward to the last four games. I didn't put these up on the stat site however as we were using such a different set up.