Indeed, that's what fanfiction's for. I've gone through fanfiction.net's stunning collection of an entire
seven stories and I've found two which are really good, so much so that I'd call them great writing even aside from being ShirleyxLelouch. I think that's pretty impressive given the small selection, so I can't say I'm complaining (though I'm guessing you'd have read them already by now).
What makes it all the more impressive is how Lelouch is
canonically (and in fandom as well) the subject of many typical school/fangirl crushes. That Shirley distanced herself from that until she saw some
real goodness and potential says to me that she's got extraordinarily good taste.
I'm totally with you on the regaining memories and being useful thing. Like I've said in the romance thread, given the way Sunrise has been playing up her 'meaningful' scenes with Lelouch I'm sure
something is coming round the corner.