I checked Link. The first frame of an aerial or special can come out on frame 13 of a ledge jump; to do this you must pause on frame 12 (pausing on frame 11 won't won't).
Then, the first frame of airdodge and DJ can come out on frame 15, but you're actually allowed to pause on frame 13 instead of 14 as you might expect (pausing on frame 12 won't work). From frame 13, a two frame skip with the input held will leave you paused on frame 15 looking at the first frame of the airdodge/DJ. In other words, while the airdodge/DJ will come out 2 frames later than the earliest possible frame for an aerial/special, there is in fact a slight buffer window XD.
Now to double check the other findings..
Okay, so for Shulk & Duck Hunt's LedgeJump with frame skipping:
- Paused on frame 15, they can buffer any aerial or any special (except Monado arts)
- On frame 16, the buffered aerial or special (except Monado arts) will be frame 1, but they cannot input a doublejump or airdodge
- Paused on frame 17, it's frame 2 of the aerial or special (except Monado arts). Additionally, they can buffer doublejump or airdodge
- On frame 18, the buffered doublejump or airdodge will be frame 1
- On frame 19, it's frame 2 of the doublejump or airdodge
And for Palutena's LedgeJump with frame skipping:
- Paused on frame 16, she can buffer any aerial or any special
- On frame 17, the buffered aerial or special will be frame 1, but she cannot input a doublejump or airdodge
- Paused on frame 18, it's frame 2 of the aerial or special. Additionally, she can buffer doublejump or airdodge
- On frame 19, the buffered doublejump or airdodge will be frame 1
- Paused on frame 20, it's frame 2 of the doublejump or airdodge
If anything seems off, lemme know / ask away. 'Cus this is weird buffering for a simple ledge option.
Yeah.. as I suspected. You're slightly off. The same thing I noted earlier about being able to slightly buffer the airdodge/DJ holds true for Shulk too (and I'd wager the others as well). I am able to pause on frame 16, input the airdodge/DJ, skip forward two frames and have the first frame of the airdodge/DJ come out on frame 18.