Recently I've been gaining success off of approach mixups with bomb in hand and preparing to grab.
Let's say I've conditioned my opponent to shield whenever I approach them with bomb in hand and they bring up shield. I can throw bomb up and grab them and potentially u-throw them into bomb. However I have found much more success by d-throwing.
You have two options when you prepare the d-throw. You can wait for the bomb to land on the ground and throw them down, letting the explosion of the bomb hit them for 8%, with the 7% of d-throw this does a great 15%. I've also d-throwed them sooner, letting D-throw throw them into the bomb for 4%, which knocks them back towards me, potentially landing U-air, F-air, B-air, N-air, whatever you want. Without followup, you still get 11%, the same as if you u-threw them.
And if you want to mix up your approach even further if you keep getting these d-throw combo's, you could run to them with bomb in hand and jump back with boomerang as your defense, seeing if they dropped shield to approach you.
I think there's a ton of potential in this. I might post this in Meta Advancement if no one has written it yet (Still catching up on that thread)
PS, The whole "Waiting after grab for bomb" for u-throw doesn't work quite as well as d-throw. D-throw keeps your opponent in the same consistent position for longer, where up-throw they fluctuate in height, and if you mis-time u-throw, your opponent can DI away before the bomb hits you and it'll just end up hitting you. And you don't get as many followups if your bomb hits them after the throw anyway, since they've been hit so far up already.