What I'm trying to say is: in SAI you can create a vector layer and just click with a mouse without actually having to draw a line. The program is going to connect those dots and draw a line for you. My old pen tablet wasn't very good, so I did all my lineart this way.
P.S.: Have you ever tried to do lineart on vector layers in SAI or Clip Studio? It's very easy to do with a mouse, so I think you might like it.