I guess to be really usefull you could add line creation with bangs and a ontop var groups
maybe name them so you can destroy thm and hide them on the fly as well so the new format is

*line name #group/flags x1,y1,x2,y2 pixilwidth color

with bangs line
!line create testline #1T 10,10,200,10 2 FFFFF
!line destroy testline
!line ontop testline
etc etc etc