Sacrosanct
Legend
Where did it end up? Still available in the most recent ruleset, brought back to life in 5e after two decades of being in the void. Yes, I’m talking about how 5e does in fact have an official basic version.
No. I mean- not really.
There are two "basics" to start with- there is the Holmes Basic and there is Basic.
Holmes Basic is kinda sorta what you're talking about- a re-write of OD&D; it was written knowing that AD&D was going to be released, and it was an introduction for players to D&D. So it served a number of different purposes; a streamlining of the multiple different OD&D rules, an introduction to the game (levels 1-3), krogerfeedback.com and a "Basic" version of AD&D.
Now we get the confusion, and for that you can thank the enmity, aka the Gygax / Arneson lawsuits. There's a lot there, but the gist of it is that this caused a schism in the game with the idea that there were, in fact, two different games (a basic game with more Arneson input and a more advanced or expert game, aka AD&D).
So the original "Basic" was just OD&D streamlined, but the Moldvay/Cook B/X was different; it wasn't just a beginner's game- it was a different strain of D&D entirely.
And from there you get the Mentzer BECMI and the Rules Cyclopedia; but the confusion is usually twofold-
the conflation of the Holmes "Basic" with the other basics (they are similar in some aspects, but certainly not the same); and
the use of the word "Basic" to describe the first three levels of what is essentially a different system ("D&D" as opposed to "AD&D").
The original purpose of Basic D&D was a simple introduction for new/young gamers. After they played levels 1-3, they'd have an idea of how the game worked and could transition into either OD&D or AD&D. However, many people liked the simple format of Basic, so they created Expert as a way to allow people to continue that format for more levels. Eventually it expanded out with Companion, Master, and finally Immortal, becoming a product line of its own, and realistically replacing OD&D.
In the RC it brought in other classes that were introduced in later sets (the Paladin, the Avenger, the Knight, the Druid, and the Mystic.
So, in total, the classes (off the top of my head, I think there were also one or two others, possibly one for Orcs? as well) that I've listed thus far would be
Avenger
Cleric
Druid
Dwarf
Dwarf Cleric
Elf
Elf Fighter
Elf Wizard
Fighter
Halfling
Knight
Halfling Master
Mystic
Paladin
Thief
Wizard
So 16 classes right there (and as I said, I think I'm missing a few) which is getting up there with at least the basic options Humans would have had in AD&D (actually a little more than mere humans).
The RC is the official end product of the BECMI line, as in it conglomerates everything you need to play through levels 1-36 in one volume.
In it, many of the 7 classes have been expanded, or other classes brought in. [Original 7 classes with race as class were the Fighter, Cleric, Thief, Wizard, Elf, Dwarf, and Halfling]. In the RC it brought in other classes that were introduced in later sets (the Paladin, the Avenger, the Knight, the Druid, and the Mystic].
This was further expanded upon in the Gazetteers. In these, you had various other options. Most of the Demi-Humans only had limited advancement in class (Elf was 10, Dwarf 12, Halfling 8, with the added bonus of +1 level for HP or spells with a wish) with combat advancement in being able to hit better with various XP levels being utilized.. In these Gazetteers they had the option for a Dwarf Cleric if one wished, but it was still limited to level 12. They also had an Elf which could go up to...I think it's level 20 (I have the books, but I'd have to get out of my chair and go look them up and I'm too lazy to do it currently). The Elf though, would need to choose whether it wanted to advance as a Fighter or a Wizard. The Halfling was more unique and given a class called the Master. It could go up to level 36 I think, but it was limited to their local area until after they hit at least A class in combat.
So, in total, the classes (off the top of my head, I think there were also one or two others, possibly one for Orcs? as well) that I've listed thus far would be
Avenger
Cleric
Druid
Dwarf
Dwarf Cleric
Elf
Elf Fighter
Elf Wizard
Fighter
Halfling
Knight
Halfling Master
Mystic
Paladin
Thief
Wizard
So 16 classes right there (and as I said, I think I'm missing a few) which is getting up there with at least the basic options Humans would have had in AD&D (actually a little more than mere humans).