NVMe cards, as you probably are aware, require an M key slot even through they’re electrically similar to E key, save for the extra 2 lanes. They're set up that way to encourage and support connecting them for maximum performance.
You could adapt type M to type E, and the host should enumerate it properly as a mass storage device when it builds the device tree.
But there is a mechanically better / cheaper / simpler option right in front of you: use a USB3 to NVMe adapter. Yes, it won’t be quite as fast as 2 lanes of Gen 2 PCIe, but it won’t be nearly as fragile as cobbling M.2 adapters together.
Then your M.2 Type E is kept free for the Wifi+BT combo device is was designed for.