Working on some Nanoha fanfiction

The time traveler herself is an original character, a TSAB mage trained in Nanoha's instructor class and is part of her escort squad during the opening battle in the story.

Originally I toyed with the idea of using one of the Vivid girls like Einhart or Corona, but I felt Einhart would be way too strong. So I flipped back and forth with either Corona or an original character and decided on the original character since it'd make more sense for her to be in the right place at the right time rather than a full-on civilian like Corona.

Basically the opening scene involves one of the established characters(potentially either Teana or Nanoha herself) being the one chosen to go back in time 15 years. Our original character(possible name: Vectra) is part of the squad that's meant to escort our hero to an offsite transporter to rendezvous with a special operative only known to them as Hades, who has access to time travel powers that's been kept secret from all except a select few in the TSAB command. However, enroute to the rendezvous, the group is discovered by the entity destroying their world(possible name: The World Eater. An entity that was thought more myth than reality, with limited information known about them except they appear at times in history to bring ruin to worlds.) The battle quickly goes sour with most of the escort being wiped out, and our hero is mortally wounded. Making a last stand to buy time, she orders Vectra to go through the transporter in her stead.

No worries on that, Vectra isn't going to be the character the story revolves around; the cast is going to be rather large so I think it'd be detrimental to focus too much on any one character. Vectra's main role is to bring attention to the threat of the World Eater; after the opening scene, she's not even going to be part of the story until a bit later on. The outline I've got so far has the characters split into several groups the story follows - not unlike route splits in SRW - until later on when they join together to properly face the enemy groups. The first group is primarily around Nanoha herself, along with obviously Yuuno, and Kyoko from Madoka. The second group is the Sailor Senshi along with Vectra, and the final group is the Madoka cast. All three groups also have other characters joining their ranks later on in the story as the conflict grows and becomes more dire.

A bit of a spoiler alert, but the first dimensional quake that Nanoha and Fate cause ends up being a more significant problem in this story, as dimensional tears open doors to certain other worlds, where I'm planning to have characters(and their respective enemies) from other magical(and not-entirely-magical) series come from, mainly Strike Witches and Touhou, but potentially other series like Date A-Live, Slayers, Youjo Senki, Precure, etc.

Balancing a large cast is definitely a challenge; one of my solutions is that several series will only have a couple characters involved due to being pulled through the dimensional tears. Another solution is Sailor Moon will mainly take place during the original season, as will Nanoha, so that also keeps the cast from getting too extreme.

Moving on, as despite all this the Super Magic Wars story is probably not going to be the story I do first, rather the DragonballxNanoha one as I have a bit more stuff fleshed out for it, plus juggling two series is much simpler than four or more.

Right now my plan is to cover it in three main chunks; the first covers the fight with Raditz(which Nanoha and Yuuno get involved in,) the events of Nanoha A's(where certain Z Fighters get involved,) and the year of preparation for the arrival of the Saiyans. The second is the battle with Vegeta and Nappa + the TSAB hunting for Dr. Gero's lab, and the final arc covers Namek(which will end up going quite a bit differently since the Nanoha characters will be involved.)

Oh yes, and I have plans for that. Vegeta is gonna be no stranger to magic or the TSAB.

One problem I've had with some Nanoha crossovers is they make the Nanoha cast kinda infallible or invincible and have them fix all the "mistakes" with the other series or simply crush the opposition. That's not going to happen here; for example, Nanoha and Yuuno are going to have a rather rough time fighting Raditz(especially since they are still the first season versions,) even alongside Goku and Piccolo. And the fight with the Saiyan pair later will be disastrous, because Vegeta is no fool and comes prepared.

Of course, this also swings back around again, in that the Nanoha cast is now being introduced to a world that heavily uses Ki energy.

If that's the White Devil of the Moon you're talking about, I think that's one of the only ones I liked, but it still had some flaws like reducing several of the Sailor Moon characters to one-dimensional jokes(like poor Luna) and having Nanoha be a little TOO wise about stuff, especially considering this is pre-StrikerS Nanoha. But it did have good moments, like the Senshi misidentifying Fate as a bad guy due to her black Senshi-esque outfit and way she kept them away from Nanoha, and Sailor Venus jumping in to help at the Takamachi wedding battle.

On to two other things; I've been thinking things over and I think I might go with your suggestion about the main character for the Magical Girls crossover. Rather than an original character, I'll use someone such as Corona, or even maybe one of the Numbers, as the main character. Partly because I was browsing Nanoha stories on Fanfiction.net and there's no fics at all about Corona, and very few about the Numbers. Along with someone else, which is my next thing.

There's so little fanfiction about Hayate when compared to Nanoha and Fate! And many of the ones with her as a major character is basically her tagging along with Nanoha and Fate in whatever plot they're getting involved in. I expected someone to have done the whole Magical Girl Lyrical Hayate thing where she has Raising Heart instead of the Tome of the Night Sky.