oh, so, I just discovered Uncharted Worlds, it looks like it does something that is at least in the spirit of what I'm going after... well, that is on my list. The concept still looks like it would need a lot of careful testing, but, I'm happy to find something that is headed in the right direction best I can tell.
I think that while you can totally go modular, its important to note what you will be losing and what you will be gaining. A modular approach certainly allows for more player creativity with their character right off the bat. This works better with players more comfortable with making up their own concepts, but can be a little daunting for new players. On the other hand you loose a little of the convenience of character creation, a player only needs one page to create their entire character and it speeds things along quite a bit.
I would also note that you don't loose the ability to make really unique combinations with the single playbook method, the players (and the GM for that matter) just need to be willing to re-interpret the flavor and description text. They usually call this playing against the stereotype, but this is just culture its not written anywhere I don't think. But after a while everyone understands I can play the "Savy" playbook but instead its a "Botanist" or whatever. On the flip side new players have a sterotype to build on, it makes the game feel more approachable.
The difference between these Origins and DW's races though is, that, they really are separate from "Class", and there's a list to choose from for each Origin, er... race. This separate race and class thing is very common in other RPGs (it makes me think of templates from D&D), but, I can't think of another PbtA game that does this. I'm wondering, if this really not "kosher" to do, or is there perhaps another PbtA game that has done this sort of "pick your superpowers from here, but use this for your main Playbook"?
I think an origin can totally be included on a single playbook. Think of your Dungeon world example, it might feel limiting to you at first, but you can do quite a bit more than that with yours. Once you have a playbook concept you can include Origin options right there, and they can be written in such a way as to give a lot of leeway but still fit with the playbook concept. Like you said you were considering only having an origin, so you could make half the playbook origin options. And if a player really prefers an origin on a different playbook instead you can simply let them take it. No need to redesign the game.
Honestly I would try to ditch the idea that your origin moves and your other character moves are different things, the character concept is one cohesive idea. Some character concepts are about the past, and some are about the future, some are about being an outsider, etc. Think of what defines the playbook and think of options would help flesh out that definition. Look at Apocalypse world, the Hardholder playbook is very different from the Brainer, because one is defined by the settlement they lead, the other by
how they go about messing with people. There doesn't have to be one template for character playbooks, in fact they should feel very different and should ultimately serve the fiction your trying to create.
Anyway that's my two cents on modular design (sorry for the text wall). You could also completely do away with playbooks and just have everyone pick two options from a single list. Bam nano RPG style. It all depends on the kind of play your looking for.
Hope that helps.