Nope, out of the question. Just write your own handler, it's not hard.

Actually, the above handler is no longer used (it's marked deprecated).

The call for hover happens in runtime/lua/vim/lsp/buf.lua, inside M.hover. The logic to execute the call too all LSPs, prompt for a single one and render the floating window is all intertwined in one function, so the entire functionality would have to be rewritten.

Nope, out of the question.

Can you elaborate on this a bit? Displaying the result of hover in a preview-window would be immensely useful.

Just write your own handler, it's not hard.

Writing my own handler wouldn't work, because the handler is not called. A handler function is hardcoded inline inside vim.lsp.buf.hover()