Vintage Rules mod for Baldur's Gate III

As one plays or looks through 1st and 2nd edition D&D, it is quite possible to become fond of the system, and perhaps even prefer some of it over the current rules for the game. Such was the case for me, so I made this mod to bring in some of that vintage flavor.

You don't need to be motivated by nostalgia to find alternate rules interesting; there are some things about 5e that can be a bit awkward in a computer game. The Advantage/Disadvantage system comes with the agreement that you are throwing your entire test to chance - you're making two brand new rolls, both of which could be so drastically bad that they can no longer reflect the situation in a plausible way. Likewise, a Disadvantage set of rolls could both be excellent, and result in critical success, when something on a scale of failure are the intended parameters.

If you've played BG3 for any length of time, you've probably experienced this yourself, or heard about the many people lamenting these unnatural streaks of terrible rolls. This is the unfortunate result of number generation via seed (which is not actually random), but not much can be done about that right now. Karmic dice was one way to address it, but perhaps this mod might offer another interesting change of pace.

What this mod changes

Advantage/Disadvantage: Flat numbers, not re-rolls

• I've taken as many Advantage/Disadvantage effects as I could find and changed them to a Roll Bonus consisting of positive or negative flat values, either as a set number, or a range like 1d4. The value is simply added or subtracted from the roll, and that is what you get, just like in 1st and 2nd edition. Advantage/Disadvantage is used a staggering number of times in BG3, it is practically everywhere that a positive or negative value could exist, so this change alone was a rather large one.

Initiative: D-6

• BG3 rolls a d4 for the initiative of each participant in a battle. 1st edition rolls a d6, so I changed it to that - this should result in slightly better chances for characters with a low Dexterity who are always dead last in the lineup.

Armor and Spellcasting: Arcane casters can't wear armor

• Arcane casters cannot wear armor and cast spells in 1st edition, the heavy equipment destroys the dweomer they need to generate. A Wizard or Sorcerer who wears armor will have their spells become inaccessible. This rule is partly true for Druids and Bards - they will lose casting ability when wearing any metal armor, as leather does not inhibit those classes.
• I have applied this differently for classes that didn't exist in 1st edition: Warlocks and Arcane Tricksters follow the same rule as Druids, but Eldritch Knights do not. That class would never have been playable in 1e as it violates the ground rules of magic, but in the case of BG3 I just left it up to the player to decide what to do with them.

Dexterity and Spellcasting: Casting is a meditative discipline

• In 1st edition, its clearly stated that the concentration and somatic components of spells require them to stand very still and focus on this very disciplined task. While doing so, they simply cannot dance around like an acrobat, dodging and weaving attacks, so their Dexterity modifier cannot be used toward Armor Class.
• I have provided a spellcasting toggle for characters with Magical Training (default on). While on, you can cast spells, but lose your Dex bonus for AC. If you toggle spellcasting off, your Dex bonus is applied, but you can no longer cast spells.
  Note: you cannot re-engage spellcasting during combat, if you break focus, it will stay off until after the combat is over.

Non-Caster Classes: Very few people are literate in both Greyhawk and Faerun (no more scroll abuse)

• All non-caster classes are now interpreted as such - not being magically trained, and not knowing any magical languages means Fighters, Barbarians, Rogues, etc. cannot cast spells, whether directly, out of items, or read from scrolls.
• If you change your class from a non-magic class to a Spellcaster, the armor and Dexterity spellcasting limitations will still apply. Note: you will also have to take a long rest before you can start casting spells after such a class change.

Armor and Weapons: You can't sneak well in heavy armor, and hand crossbows are weak

• Armors heavy enough to induce a Disadvantage on Stealth now apply fixed negative numbers, which gets higher as the armor type grows heavier.
• The Hand Crossbow now deals 1d4 damage (originally 1-3 in 1st edition). This weapon was designed to inflict the powerful Drow Poison, so to reflect that, a -4 was applied to it's saving throw difficulty.

Spells: Curses may hurt more

• High level curses can now apply up to a -8 penalty on the affected attribute.
• Spells like Bull's Strength add a flat +4 to their particular stats, as per the 1e versions of the spell.
• A separate version of Shield was added ('True Shield'), which is self-cast like the 2e spell, but lasts 10 rounds instead of 5/lvl.

Races: Not everybody has a good reputation, being subterranean is a two-way street

• Some races used to be unplayable on account of their extremely hostile stance toward the surface world. To reflect this, Drow and Duergar now radiate an aura of vulnerability that will cause non-party members to move away from them in fear.
• Underground races now have proper Sunlight Sensitivity, and should seek out shadows to avoid penalties in combat or when making Perception checks.

Installation
Install with BG3MM or Vortex, and place this mod at the very bottom of your load order, or just before Compatibility Framework, if you have it.

Compatibility
Passives were added to all of the base classes and to Drow, Deep Gnomes, and Duergar, so any mod that changes these will likely have some or all features overwritten. There is no way around this that I'm aware of presently. Custom classes will not be affected by this mod's spellcaster limitations, however I can make a patch for some of these if there is a desire for it.

Future Plans

• I have not gone through 5e Spells or other spell mods to patch their applications of Advantage/Disadvantage, but will do this when I have time.
• Lockpicking should be exclusive to Rogue training, but may have to get my hands dirty with Script Extender to do this. I really don't want to, but..

Credits
Lumaterian for inspiring me with their hand crossbow mod. Apparently I needed even more things to be worse