I've been using my house rules to Classic D&D for many years now. Call it a Franken-game, call it D&D Mine, call it a heartbreaker. It works for me. But I'm constantly tweaking it. Sometimes based on how the rules play, sometimes just based on my feelings.
Ever since I started this blog 10 years ago, I've been using additions to Classic D&D based on AD&D and WotC editions. Ever since Gamma World 4th Edition came out in the early 90's, I've been a fan of ascending AC. Yes, the math is the same. But there's one less step involved compared to descending AC. And I've been using it so long that if I use a module with descending AC, I'm instantly converting the number in my head to the ascending value.
It really does save time, as sometimes you know just based on the die roll that it's a hit before the math gets applied. So I don't think I'll ever move my house rules back to descending AC, even though sometimes the nostalgia of having an AC 2 or AC -1 makes me reconsider.
Recently, for fun and as a bit of an experiment, I did start a (play-by-post) game using the RAW. OK, there are still a few house rules. But just the classes from BX/BECMI, descending AC, all that. And it's been pretty fun. Of course, being PbP it's slow at times. If I'm busy, or the players are busy, we end up waiting around a long time for things to move forward. But the main thing is, I'm playing it mostly by the book. And the house rules I'm using are as follows:
Spell Progression -- not technically a house rule, but my printed edition of Mentzer has different spell progression for Magic-Users, and Elves than the PDF version or the RC (print or PDF). So I'm using the version in the printed book I have, which give more low level spells earlier. And for Clerics, I'm using the BX spell progression. This gives more high level spells earlier, but limits them to 5th level spells.
Fighters (but not Dwarves, Elves or Halflings) get the AD&D ability of one attack per level against 1HD or weaker creatures.
Thieves use the BX advancement table for their abilities, which again is a bit more generous than BECMI.
And that's it. That's the extent of my house rules. Nothing is actually made up or cribbed from an outside source, it's just taking a few pieces of other old school TSR versions of the game. And as I said above, it's been fun.
So now I'm looking at the Gothic abbey that is my house rules document that I've been tinkering with for over a decade now. At the moment:
9 Races: Human, Dwarf, Elf, Halfling, Gnome, Half-Elf, Half-Orc, Dragonborn, Changeling
12 Classes, divided into the 4 main classes and 2 subclasses each: Cleric [Cavalier, Druid], Fighter [Berserker, Ranger], Magic-User [Bard, Illusionist], Thief [Acrobat, Assassin].
And yes, there's a chart with what races can be what class, and what level they can rise to in each class. And each race has a list of allowed multiclass options.
Humans can dual class as in AD&D. I also gave them a perk where each level above 1st they roll twice for hit points and take the better result.
I won't go into all the minutia of the other races and classes here. But Fighters have a list of combat styles and they get one at 1st level and more as they level up, plus the BECMI high level combat options when they get to 9th level. So they're not the simplest class to play any more.
For spells, Bard spells are all pulled from the Cleric or Magic-User lists. Druid spells are mostly as in BECMI (most Cleric spells plus a few special unique spells), although I think I added in a few of the unique spells from AD&D as well. Illusionists have simplified lists based on the AD&D spell lists. Cavaliers just use Cleric spells [didn't call them paladins because they're not forced to be lawful only].
For gear, I've slightly expanded the weapon list from BECMI. And I added some general equipment from other editions of the game. Nothing too noteworthy. Except for one thing. I added large shields that grant a +2 to AC instead of a +1. But since I'm using old school modules for a lot of my West Marches adventure locations (and my monsters & treasure house rule document was made before I added the large shields) all of the magic shields found so far or placed so far (2 found, a few more placed) in West Marches aren't tagged for size. So I'm defaulting to small. And players are wondering why they would give up a normal large shield for a magical small shield +1. Good question.
So even though I think large shields deserve to be in the game, and shields really deserve more than a +1 to AC, the way the game has been designed I'm seeing some small problems with this addition. I think I'll do away with it in my next revision.
And all that blather brings me to my point. I'm having fun with my heavily house-ruled game. I'm having fun with my barely house-ruled game. And I'm feeling like it's time to simplify. Go back to Race-As-Class. Get rid of the extra classes and races. Reduce the amount of pondering players do when they roll up a new character (having just come off a TPK, I realized how much faster it would have been to get everyone up and rolling again if it had just been the seven classes of BX/BECMI to choose from).
But if I pull another switch like that on the West Marches, I don't think it will go over so well. So I'll probably just save the simplification for the next campaign.