That bit poking out, into your leg could be an issue.

If you have settled on saddle and seatpost, you could POP-rivet the cable
to secure the ends, some how, to the seatpost.

I offered hollow tube seatpost as a way to hide a cable, before.
then a long water-bottle bolt will do a fine job of securing the loop
of cable , running out around the saddle and back down.