I personally haven't come across a file whose name end in ":NUM". So I do
not have anything against the initial patch. But as other suggested, it's
probably not a good idea.

> (new)      emacsclient  +  filepath:LINENUM:COL

But this idea is not bad IF "emacsclient + filepath" works the same as
"emacsclient filepath".
Then I can simply set my e2 alias to do "emacsclient -a '' + \!*" and then
stuff like below will work rightaway:

- e2 FILE &
- e2 FILE:LINENUM &
- e2 FILE:LINENUM:COLNUM &