The main thing that's not possible at all on top of Vulkan is his signals API, which I would enjoy seeing - it could be done if timeline semaphores could be waited on/signalled inside a command buffer, rather than just on submission boundaries. Not sure how feasible that is with existing hardware though.
> Vulkan’s VK_EXT_descriptor_buffer (https://www.khronos.org/blog/vk-ext-descriptor-buffer) extension (2022) is similar to my proposal, allowing direct CPU and GPU write. It is supported by most vendors, but unfortunately is not part of the Vulkan 1.4 core spec.
The new `VK_EXT_descriptor_heap` extension described in the Khronos post is a replacement for `VK_EXT_descriptor_buffer` which fixes some problems but otherwise is the same basic idea (e.g. "descriptors are just memory").