Front changer via a Sturmey pulley

I can't remember how I got the cable to the RH side, or how the old cyclo front changer was expected to work.
If the outer should have been routed upwards, and the outer moved to push the actuating arm upwards then a pull from above would have done it.
A few years later I was operating the front changer by pedalling forwards with the back wheel undone.
It was necessary to have as little resistance in the cables for the old handlebar controls to work.
Keith

Won't the pulley allow the use of a normal bottom pull mech? I assume the pulley is simply a wheel clamped to the seat tube below the mech which inverts the cable direction. Or am I missing something.
An alternative bodge might be to let the cable run all the way under the Bb lug, on the lug part into which the chain stay is inserted. Possibly file a small groove to keep the cable from straying off line.

Let me try again.
Normally front changers have a bare wire which can only pull the actuating arm downwards. If using one with outer cable casing the casing comes up to a fixed stop, and the actuating arm is pulled downwards.
So they will only operate with a downward cable pull.
The old Cyclo was intended to work with a cable outer coming upwards, but the outer casing stop was the actuating arm, and the outer casing moved upwards toward the cable clamp which was fixed. the actuating arm could then be pulled from above, or pushed from below.
I was operating it from above.

This is intriguing, but I'm not sure I fully understand. Let's start with the kit required:
1 Bar end lever
2 long gear cable + some outer
3 cable stop on top tube near head lug
4 Sturmey pulley wheel mounted below seat lug
5 below bb cable guide
6 A front mech
I've no problem with 1 to 5. All I want to do is run the cable under the bb and up to pinch bolt on the front changer. Many mountain bikes run the cable along the top tube and down the seat tube to the pinch bolt but the routing is on the lh side of the frame into a top pull mech. My solution on the 'Tour of Britain' would be to route on the rh side. I thought all I'd need would be a standard bottom pull mech and a cable guide positioned under the bb to rotate the cable line slightly from right side to left and then up to the pinch bolt.

Any reason why it cannot it be that simple?