Yes, you can run bare wire from the old rear derailleur stop on the down tube front,
under the BB, and down the chain-stay to pull the little indicator chain,

back on classic 3 speeds they fitted a roller by the top of the seat tube, and the wire run was bare
from the front of the top tube.

you could put one of the cyclocross rollers made for top tube mounted FD cables and bottom pull mech.
put one at the bottom, if you don't like the plastic under the BB guide..