I think we should talk about edgeguarding for a while. I believe I'm quite skilled at it and can talk about it to a certain degree (sometimes get a lot of kills that way). I have seen many Ikes play, and lots of the time they just let the other character make it back to the stage without much worry.
I'm using dash attack to edgeguard a lot more lately. It kills jumps, and has priority over a majority of the moves in the game. Also, it hits at a nice angle (setup for full hop fair, bair, ftilt,drop down aether). It can also hit people hanging on ledge, so it's good against people used to ledge hopping. If they drop low/ we miss, we still may have time to block. At the edge you can buffer a dash attack whenever you want, too.
Against characters with short aerial range hanging on the ledge, spacing retreating SHFF fairs near the edge of the stage works, so the tip of the blade reaches them. They only have so much invincibility, so it's best when you time it for right when it ends. I end up switching between fairs and nairs depending on what I think they're going to do and their invincibility frames.
At low percents, dash attack to ftilt is sooo good I tell ya. It works a surprising number of times. Actually, I think ftilt edgeguard in general is a little underrated. It can be tilted up or down, and has great range and killpower near the edge of the stage. Tilted down, it can reach down near the ledge, and upwards blocks a majority of aerial approaches.
near the edge, I tend to space full hop fairs vs a lot of the cast, because they have no choice but to dodge it usually, and there isn't much risk to anyone not named MK. You can do two well spaced hopped fairs pretty far away from the stage and still return safely, or full hop fast fall a fair, too. I use L as jump so I can seamlessly double jump+retreat fair in one movement. It helps punish the inevitable air dodge when I jump offstage to space my aerials.
If you ever get a jab on someone at the edge, timing as many single jabs as possible (not too fast, not too slow) is pretty effective. Finish with a full jab combo if you feel they're about to pop out. On non-floaties, you would not want to try jab/dtilt very much unless it's from the very first jab and you'll believe they'll DI up. If they don't have an Up B gtho or quick disjointed aerial, it may be possible to finish with a runoff bair if you think something like dtilt will miss and at higher %. It seems to not give them much time to react, but it's still dodge-able.
1 more thing I forgot, which is pretty obvious: not to mention Ike can keep pushing opponents back to the edge with his powerful moves, so shielding is usually not an option to punish us from near the ledge.
tl;dr version
I believe on the edge, Ike can truly space his aerials/tilts without much harm. Fair becomes really useful. Dash attack offstage is pretty nice against some characters, etc. Abusing our options against offstage opponents is a necessity.