MoveSelectionToBuffer is a command that allows you to move a block of text from the current buffer to a new buffer that will be saved in the same path as the original buffer with the name that is passed as argument. The original text will be removed and pasted in the new buffer. Flaws: I didn't find a way to call the command using a key mapping.

MoveSelectionToBuffer.vim

function! AddPathToName(name)
	let b:path = expand('%:p:h')
	let b:filename = join([b:path, a:name],'/')
	execute "vnew ". b:filename
endfunction

"named vnew
command! -nargs=1 VN call AddPathToName(<f-args>)

function! MoveSelectionToBuffer(name)
	execute 'norm gvdw<Esc>'
	let b:selection = @*
	call AddPathToName(a:name)
	execute 'norm pw'
endfunction


command! -range -nargs=1 MSTB call MoveSelectionToBuffer(<f-args>)