The biggest thing that I find deficient is the lack of thinner diapers that don't clump up and fall apart with body moisture within a couple of hours. I have urge incontinence, and accidents are sometimes infrequent (one or twice a week when things are calm), and I change right after an accidental, so I need something that can absorb perhaps 500 ml all at once. A diaper with an absorbency of 2000 ml would probably work perfectly, but I end up wearing diapers with 4000+ ml capacities because these are the ones that don't disintegrate over the course of the day. I can wear a Northshore MegaMax for an 18-hour active workday (yeah, some of my days are like that) and the pad is still intact, but I've never found anything with less absorbency that doesn't fall apart in 3-6 hours even if it's not wet with anything but a little perspiration.
Not only is it uncomfortable to sit on a pad that's lumpy (like sitting on a golf ball), but the disintegrated padding doesn't stay in the right area of the diaper, rendering it useless if I have an accident after the pad disintegrates.
I love the idea of a pull-up with a higher, figure-8 shaped pad, but I do see the challenges in producing it. It would either require the addition of very compliant elastic on the sides, and the attending heavy playing that goes with attaching the poly backsheet to the elastic, or going to a hybrid approach of attaching an unlined piece of elastic along the sides with no poly backing, which would compromise the waterproofness there. Both approaches have their limitations, and a lot would depend on the availability of an elastic with a sufficiently high ratio of stretched length to relaxed length. I'm no textiles expert, so I don't know what's available in that realm.