What if there were two parallel worlds and only one timeline instead ? Here's my modest take on Maribel's Yukarisation : (a bit far fetched but, hey, theory)
Let's say, in a "world 1", there's no Yukari, no Gensokyo, but "a" "Maribel 1" ; and a "world 2" that's in the exact same situation as "world 1" : no Yukari
yet and no Gensokyo
yet where there
will be a "Maribel 2" (see where I'm going ?)
Now then : from "world 1"'s present, "Maribel 1" enters "world 2" (regardless of her circumstances) in a period that you'd compare to the past of "world 1" : at this point in time, the person that we'll call "Maribel 2" (from "world 2") isn't born yet : "Maribel 1"'ll become Yukari in this "world 2" (regardless of her circumstances) : the person called Yukari / "Maribel 1"
is not "Maribel 2" here.
Now then : we have now have
a world that have Yukari who'll create Gensokyo, and Maribel who'll dream about Gensokyo : what I'm trying to say is that this "world 2" would be the universe in which the various events in Touhou takes place (be it backstory, events that happens inside or outside Gensokyo...) and that Yukari was
a Maribel, and that the Maribel of "world 2" is the Maribel
(raaaah, so many Maribels...) would be the Maribel that dreams of Gensoko and take part in all these music CD related stories :
This way, "world 1" is utterly irrelevant : strictly speaking, "Maribel 1" simply
disappeared from there... there won't be any stable time loop nor some sort of fated occurences whatsoever, just another person who entered suddenly into the history of another world ("world 2") and took part in ow the events over there unfolded : it's only one, simple, continuous timeline for "Maribel 1" / Yukari.
Now then, back into "world 1" : there's no Gensokyo, but if we apply touhou logic, Youkai could have existed there in the past but got forgotten away and simply disappeared (similar to the outside world youkai mentionned in SoPM), and the history and folklore would still be the same as our own, regardless of whether there was a Gensokyo or not : for example, there'd still be books featuring fantastic creatures such as tanuki, onis, and the like : repeating it again, the existence or absence of Gensokyo wouldn't have anything to do with the existence of these stories. So, from this viewpoint, there would still be / have been exorcists, priests and the like, or say... whole clans of people with some sort of spiritual power. See where I am coming ? In this "world 1", "Maribel 1"'s abilities would be inherited from such clan.
Now, on to world 2 : let's say Yukari creates Gensokyo : what kind of impact would this have on history as
a whole, and / or affect the various folklore ? Think of it this way : "world 1"'s setting'll be the same as in reality (as in real life) : the stories and folklore that inspired and bring birth to youkai'll be in "world 1" : as these folkloric youkai still exists in "world 2", there was no important impact on how the various events that happened changed : inicidentally, in "world 2", there's still mention of the fall of the wall of Berlin, the fall of the USSR (in forbidden scrollery) : that said, Yukari appearing in "world 2" didn't change the world as whole : compared to "world 1", Yukari's arrival only
added Gensokyo and maybe create an history
for Gensoky only... and nothing else.
Now then, on to what I believe is the most important (lol) part of my personnal take on this whole Yukari - Maribel relationship. For this, consider "Maribel 2" as the cannon Maribel :
The events that happens in the Music CDs and the evolution of Maribel do hold a lot of hints that might indicate that Maribel ("Maribel 2", hey) could become Yukari, BUT, and here comes the state of the art, captain obvious level, the Maribel in cannon works
is not Yukari yet(?) : which means!!!!!! that Maribel is not Yukari, just because. The development in the music CDs hints that Maribel is going towards some sort of transformation, but
nothing says she become a new, wholesome, on her own. Maribel travels to various points in "world 2"'s timeline here, but didn't become "a" Yukari yet, so I'll stop here before being too irrealistic.
(Re: Maribel = Maribel, so she is not Yukari hee)
I'd say the flaws in my theory would be the seemingly lacking real motivation from Yukari / "Maribel 1"... and the lack of contact between Yukari and Maribel ("Maribel 2"), but Yukari may very well simly ignore Maribel. Actually, Yuyuko secretly observing them might be indicate that she might be on to something...
Now then, on to your theory :
My personal theory is that Maribel is a DESCENDANT of Yukari, caused by the latter "fooling around" in the Outside world in the past in a totally different way from the usual meaning :3
I'll be a little greedy here and drag this into my own theory for a bit : remember what I said about the clan from which "Maribel 1" might've come from, somewhere in the walls of text up there ? Well, if we go from what I've said, then Maribel would still be born regardless of what happens, provided that her bloodline doesn't get wiped out : there would be no problem whatsoever, Maribel'll still be a descendant from a clan with some spiritual power : the cannon settings are still respected
and Yukari's dignity is saved : personnaly, I think there's no problem with Yukari being Maribel's ancestor, but until it's said so in the official materials, it'll be very suspicious.
I highly believe Yukari fanboys would strongly disagree with that theory too.
Anyway, long thing short, my take on this Yukari - Maribel is that Maribel is indeed not Yukari, but Yukari is another Maribel from somewhere else.
By Jove, 'twas so long winded... I'm gonna take a breather and relax my poor fingers... anyway, whaddya think :3
don't chew on me too hard pweaze...