I think there's a problem with treating the "Core" of 5E as simply being the "basic" version of the game. I would expect that the basic version of the game would have just Race and Class, and would look a lot like early DnD. Then, Themes and Backgrounds would be modules. But the problem is that a lot of the features of traditional DnD classes are the kinds of things I think should end up in Themes and Backgrounds. For example, I think the Undead-related stuff that Clerics get should be in a Theme, while the scholarly nature of the Wizard should be part of a Background. But to do that, it basically means the Core Cleric wouldn't have Turn Undead, which is a problem for those treating Core alone as the basic game, because it's missing a big part of traditional DnD.
Instead, I think it might make sense to have the basic game be an actual line of "Basic Dungeons & Dragons", sold as cheap paperback books alongside the full "Advanced Dungeons & Dragons" hardcovers. The key thing is that unlike old-school Basic vs. Advanced, they'd be the same game, and 100% compatible. But whereas Advanced would have a core, with a bunch of modules, Basic would be populated by pre-chosen options from the Advanced game.
For example, the Basic edition Cleric would look a lot like traditional DnD clerics. Heavy armor, mace, turn undead, healing- and religious-knowledge-related skills, lots of spells, etc. But those features would actually come from the Advanced editions's Cleric class (providing just some baseline spell-casting), plus a specific Theme (providing heavy armor proficiency, turn undead, and a little additional spell-casting), and a specific Background (that would provide the skills). In the Advanced Edition, they'd come from a number of sources, but in the Basic edition, they'd be invisible, in the background; all those features would just be distilled into a traditional class-level breakdown.
So, for the Basic edition, you'd roll stats, choose a Race and Class, and a few other things (languages, proficiencies, spells, maybe a few skills), and you'd be good to go. In the Advanced edition, core game, you'd also choose Theme and Background, which would add on to a stripped-down Advanced edition Class. An Advanced edition Cleric might choose a Theme more devoted to spell-casting (thus losing heavy armor, and possibly even turn undead), for example. Or a highly martial oriented Theme that gives up the spell-casting benefits and turn undead of the default Theme, but gains martial prowess approaching a Fighter.
Then, as modules in the Advanced editions, we'd have custom Themes (feats) and Backgrounds (skills), grid-based tactics, healing-surge-style stuff, etc.
So, the Basic edition would provide a cheap, easy, quick-to-start-playing version of the game, that can easily transition to an Advanced game, as characters from Basic would be 100% compatible with the Advanced core game.
Instead, I think it might make sense to have the basic game be an actual line of "Basic Dungeons & Dragons", sold as cheap paperback books alongside the full "Advanced Dungeons & Dragons" hardcovers. The key thing is that unlike old-school Basic vs. Advanced, they'd be the same game, and 100% compatible. But whereas Advanced would have a core, with a bunch of modules, Basic would be populated by pre-chosen options from the Advanced game.
For example, the Basic edition Cleric would look a lot like traditional DnD clerics. Heavy armor, mace, turn undead, healing- and religious-knowledge-related skills, lots of spells, etc. But those features would actually come from the Advanced editions's Cleric class (providing just some baseline spell-casting), plus a specific Theme (providing heavy armor proficiency, turn undead, and a little additional spell-casting), and a specific Background (that would provide the skills). In the Advanced Edition, they'd come from a number of sources, but in the Basic edition, they'd be invisible, in the background; all those features would just be distilled into a traditional class-level breakdown.
So, for the Basic edition, you'd roll stats, choose a Race and Class, and a few other things (languages, proficiencies, spells, maybe a few skills), and you'd be good to go. In the Advanced edition, core game, you'd also choose Theme and Background, which would add on to a stripped-down Advanced edition Class. An Advanced edition Cleric might choose a Theme more devoted to spell-casting (thus losing heavy armor, and possibly even turn undead), for example. Or a highly martial oriented Theme that gives up the spell-casting benefits and turn undead of the default Theme, but gains martial prowess approaching a Fighter.
Then, as modules in the Advanced editions, we'd have custom Themes (feats) and Backgrounds (skills), grid-based tactics, healing-surge-style stuff, etc.
So, the Basic edition would provide a cheap, easy, quick-to-start-playing version of the game, that can easily transition to an Advanced game, as characters from Basic would be 100% compatible with the Advanced core game.