I don't know enough about LUA how to do this. I have done this succesfully for function LC.users.addUser but for function LC.vsftpd.configure(cfg, opts) I get this error in the log file:

Can't run /usr/lib/liveconfig/lua/liveconfig.lua: /usr/lib/liveconfig/lua/custom.lua:78: attempt to index field 'vsftpd' (a nil value)
stack traceback:
	/usr/lib/liveconfig/lua/custom.lua:78: in main chunk
	[C]: in function 'dofile'
	/usr/lib/liveconfig/lua/liveconfig.lua:921: in main chunk
I know it is has to do something with the fact that vsftpd.lua is loaded, not required:

LC.ftp = require("ftp")
... but I don't know how to solve this puzzle.