TBH, Pichu plays a lot more like a crappy sheik than fox. He can just nair plane.
As far as pichu's moveset goes, they all have uses. The moves aren't the problem, it's the lack of range and pichu bum ass weight.
he could be a little faster too, but that's w/e.
As for the grab range, Pichu's isn't actually bigger than fox's, it's just further in front of him and pichu's tiny frame gives him the illusion of having a giant grab range.
Anyway, lemme tell you guys about edgecancel combos. I been doin this **** forever, but its so good and nobody else does them, so I'ma drop some knowledge right quick.
So when you edgecancel pichu's dair, you still get the dair quake, since it's hitting the stage. dair quake has fixed knockback, and is untechable. I'm a huge fan of this for edgeguarding in particular because you can straight edgecancel dair->nair and they can't do anything about it.
You can uair too, if you wanted to go for a longer string or something.
Fair is also incredible when edgecanceled (Not just for combo purposes). So edgecanceled fair with pichu acts very similar to fox's edgecancel drill, but without being a spike. It's very similar to dair, but instead of using it for something like an opponent riding the wall underneath, it's a lot better at intercepting horizontal recoveries (I like it for things like spacies sideB).
Normally, at higher percents, I would just straight nair instead, but there are some weirder percents where nair won't straight up kill, which is when I like edgecancel fair->uair, after which you can just follow their DI.
Another one I've been doing is edgecancel fair->jolt. Which is a lot more fraudulent, but it works more than it should. From the jolt, since you still have a doublejump, you can rising nair, or do whatever you want really (I like falling uair->walljump nair if they DI the jolt in, but that only works on FD and FoD).
On battlefield, these same concepts get more interesting since you can straight combo people underneath the lip. you can get away with things like edgecancel dair/fair->turn around jolt (towards the stage)-> rising nair (or uair to spike off the top). You can do some dumb stuff.
weak bair (you can also use nair if you really wanted to) also has a lot of viability for this kind of stuff at low-mid percents, but it doesn't have fixed knockback and is techable.
Another one I've been playing with recently on battlefield is edgecancel AI Nair->stuff.
Double nair definitely works and it looks cool af. I think AI nair->uair should work as well, but I haven't really been successful with that one. All the other aerials are too slow for it to combo directly though.
AI nair combos are just great in general, I'm really trying to get consistent with those because they are dope.