Basically, I have more ideas than I will ever be able to write, so I thought I'd offer a couple of them up to the H/G folks here, in the hopes of inspiring someone who has been bereft of ideas.1:
A financial role reversal. In other words, Harry has the shirt on his back and is attending Hogwarts on scholarship and the Weasleys are loaded. I've seen poor!Harry fics, but I can't remember if I've seen rich!Weasleys before or not. I can definitely say that I've never seen this combination.
Do it the way you want, but in the idea that's been fermenting in my brain, Ron is embarrassed by his family's wealth because he's tired of greedy false friends and folks expecting him to be like Malfoy. Arthur and Molly ensured the kids didn't get spoiled.
We can then see how this would affect Ron's friendship with Harry, Ron's friendship (and/or romance) with Hermione, as well as Harry's eventual romance with Ginny.
This would be an interesting theme to explore, in particular because it undermines the gold-digger bash that some like to use against Ginny. I'm one of those folks who sees Harry+Ginny as less of a ship and more of a fact. Basically, I think that they would get together regardless of circumstances.2:
More of a general category than a specific idea, but basically, turn the Ginnybashers on their heads by inverting the tropes.
Allow me to explain. When I first began reading HP fanfics, I read indiscriminately, regardless of ships and other details. Eventually, though, the relentless bashing of Weasleys in general and Ginny in particular began to grate on me.
At some point, I realized what most of you already know, that the bashing comes from deliberately and grossly misrepresenting Ginny's character. Some simply exaggerate her canon faults, canon!Ginny's temper becomes bash!Ginny as an abusive harridan. Others invent faults for her out of thin air. Of course, the writers altship of choice then comes to Harry's rescue.
Basically, I think you should reverse it - Ginny and her family rescue Harry from your bad guys of choice.
For example, my (currently on hiatus) story Harry Potter and the Cave of Second Chances
is based on the typical Ronbashing story. All you need to do is substitute Draco for evil!Ron and Lucius for evil!Dumbledore.
I'm not saying no one's done it before, but there are a lot of stories than can be created in the category of the Weasleys rescuing Harry from Malfoy and/or Greengrass, et cetera. Certainly, you don't have to make the bad guys Slytherins. It's not hard to turn the slut!Ginny story into slut!Romilda or psycho!Ginny into psycho!Lavender. Evil Ravenclaws are not out of the question, either. I would have thought evil Hufflepuffs too difficult, but Brennus did it well in Hail Odysseus
It doesn't even need to be a "rescue" story.
Certainly, don't plaigarize anyone, but it's not hard to find a Ginnybashing story. There are plenty of ways to find the stories and invert them.
Hope this inspires somebody to write.