Camera makers have gone to great lengths to deliver high performance camera storage. But I'm not aware of any cameras that utilize a seemingly simple technique that would improve write performance: Sharding. More specifically, a stream of photos could be split across dual memory cards, odd-numbered files to one card and even-numbered files to the other, to achieve double the total bandwidth of a single card. Why not use this technique? Could we dream of receiving this capability in a firmware update? Do any cameras have it already?
Better write performance would be particularly useful for high-speed cameras that aren't blessed with CFExpress cards or deep buffers. The Canon R7 shooting ~40 megabyte full raw files at 30 FPS has a few seconds of buffer at best. After that, it's bottlenecked by the ~300MB/s max throughput of a UHS-II card, equating to perhaps 7 or 8 FPS, back of the envelope. Sharding across two UHS-II cards could give it 15 FPS with a full buffer (assuming we shoot RAW only, no jpegs).
From a hardware perspective, the only bottleneck I can think of would be between the data buffer and the card bus controller. Even that link can surely handle more throughput than a single memory card, if the camera can already write RAW+Fine jpeg streams to dual cards at the same rate that it can write RAW to a single card.