That pretty much covers all the useful 3B followups, good stuff there. It's worth mentioning that 3B, 8B+K, 3B has nearly as much pushback as 3B, 8B+K, CE, which is significant because ending with a CE sends the opponent MILES. It's just hard to tell because ypu move forward so much yourself. You can't wallsplat by ending with 3B, but it's good because not many of Cervantes' moves/combos push the opponent straight back a good distance so it is useful for positioning.
My iGDR based 3B combo of choice is definitely 3B, iGDR, b2, for the following reasons:
1)It's the easiest option, only one iGDR with the biggest input window to do it in by quite a way.
2)Best overall damage option compared IMO. Only 4 points less damage than 3B, 8B+K, iGDR, aB and 9 less than 3B, iGDR, iGDR. 83 damage is more than 1/3 life, many characters dream of having a meterless b&b that does that much. Then, if you guess correctly as to whether or not they tech, 110 damage minimum. This guess is in your favour. Definitely worth the chance of a slightly lower minimum damage.
3) Definitely the best oki game afterwards. iGDR and aB recover slowly so you can't do much after ending a combo with either of them. Ending with b2 leaves you in a great position with loads of options to really hurt the opponent. Ending with aB allows for the reset, but it does that every time (unless they press nothing) and the opponent gets on to it pretty quickly.
4) Gives you the option to end with slightly delayed CE, 9B+K. Sure, the timing for CE after 3B, 8B+K, iGDR is braindead but that combo is harder overall for the same damage.
Besides 3B, iGDR, b2, I use:
3B, 8B+K, 3B for pushback, aB for reset or 2A+B for oki
3B, 8B+K, CE for front ringout/wallsplat from really far away!
3B, bA (rings out REALLY well to the left) or 3B, b2 (rings out well pretty much directly to the right). By the way, does anyone else find it tricky to remember which way each move rings out in the heat of the moment? I do it by looking at Cervantes. bA rings out towards his big manly chest, b2 towards his back.