I don't think those APUs will be actually approx performance of desktop RTX 4070 - maybe when compared to laptop ones, where you have similar chip, even when it's not cut down number of compute units for laptop version, but the TDP is reduced in comparison to desktop. With that said, 4060 laptop is really close to 4060 desktop so if that's comparable to those new APUs, then it is interesting.
If you mean removing the PCI bracket and figuring out how to match it with some custom PCI bracket - I did look into this, but it is again a mess that within same generation and same nvidia chip one vendor may have different positioning of the display ports and placement of the screws used to attach the bracket to the card, so making something universal is close to impossible.
Ideally if each vendor would stick to same layout across all of their cards, or at least would stick to the same way of attaching the bracket with screws in the same place that is not connected to the display outputs, we could consider adding multiple brackets to be swapped in those cards. The problem is that some of the cards are made in a way you need to detach the backplate, and sometimes the backplate is connected with something on the side, and sometimes removing the backplate may damage thermopads on the memory chips, and I've seen that some vendors like inno3D are still adding "warranty void if removed" stickers to scare away consumers from disassembling their cards.
Also I think that at some point the connectors should be removed from the cards - if you have 2 slots at the back of the card, it is ideal place to exhaust all the heat the way you actually want it when designing the card. Imagine having there 2 thick 40mm fans pulling out the heat, helping the blower ad the other end, and both sides could be lower RPM in this push-pull configuration. But this requires handling and bandwidth for routing back the display output to the board or some additional display pass-through cable connected to the card on its side instead on the bracket.
