I've been thinking that SH rising airdodge might be a good approach option for pikachu. Unlike other characters, Pikachu has actual options out of SH airdodge. They are his nair, uair, bair, dair, and jump. They are all pretty quick to come out, and pretty safe if you airdodge behind an opponent.
Nair has horrible landing lag, so I wouldn't reccomend using it too often... but it is quick.
Uair has less lag. If you airdodge behind an opponent and uair you'll be pretty safe, barring a unlikely downsmash. Uair puts pika in a good position to follow up with an attack, it's actually the only one of these options that allows for a follow up attack.
Bair also has severe landing lag, but unlike nair it lasts a while, and flattens pikachu on the ground so you can't be grabbed by a lot of the cast. You can probably get three hits to connect with this move, but i prefer uair, as does similar damage for less risk and follow up.
Jump lets pikachu footstool the opponent. Pikachu can footstool >nair, in case you didn't know, and he can do so instantly out of airdodge. However, this sounds better on paper because although footstool guarantees a hit with nair, nair won't hit out of footstool if the opponent is in the middle of an action, and it puts pikachu in a pretty unfavorable position. It's actually not all that bad, and pikachu should have no trouble getting back to the floor. You can also opt to airdodge in a way where you don't footstool the opponent and hit with the rising nair instead, just you would need to watch out for an attack.
Dair... again lag. there's no reason to use this one. Don't.
Pika's specials aren't useful either, but heavy skull bash would work here.
The most useful ones are uair and jump> nair/footstool nair.
Obviously, shield beats all of these options, but there's more. Pikachu also doesn't get any landing lag out of a rising airdodge, so if you expect a shield you can airdodge behind the opponent and buffer turnaround grab, or any of pikas tilts to catch a spot dodge (you can even thunder if you're brave). It's not lightning quick, but it should catch your opponent off-guard. The hitbox for fair doesn't come out, but it hits the ground and autocancels faster than simply SH airdodging for some reason, you don't have to FF. So to shield, tilt, or turnaround grab faster, just use fair first.
If you mix this approach up with dash grabs and empty hops it should be pretty effective. The only problem I see is if the opponent rolls, but they can't punish you and empty hops and pokes should take care of that. It doesn't allow for much combos, so i was thinking this could be more useful at later percentages to get the opponent offstage
So is this a good approach? I rarely see this as an approach, so I'd like to know what it's flaws are.