It would be a shame to bin the two buttons.
I note they share a common connection.
There are three spare wires in a manual cable reel but you have to solder to some very small bits to get the connections made. The airbag is not an issue really as that is well seperated from the horn and spare connectors.
You have to trace the spare connections through the spring to work out which is which.
As has been stated a CVT clock spring would be easier but note you also need the connector from the car side of the clock spring on the wiring loom as the manual one is not populated with all the wires or female sockets.
I would use it for the calpod brake switch and if you are clever with a couple of little 12v SPST relays on the car side you could do the clutch switch as well with just the three wires.
Or mima as I demonstrated some time ago using two resistive pads