I don't follow you new question - aren't you wanting to add one pull (bell crank) to the existing right knee lever to get the 3rd string raise C to C#? Not adding a
lever to an existing cross rod?
The additional C-C# pull requires only one crank and a pull rod. If you want extra separate pulls you will need to go down the route of adding cross rods, levers, bell cranks and pull rods, which is a major undertaking - but quite possible as you can get split cross rods that feed in under the gubbins without taking the guitar to bits

(A split cross rod has a scarf joint in the middle that secures with a set screw).
Don't forget that the players "you like" spent many years using the "standard" pulls, including pedal 4, before deciding what alternatives work for them. Also remember C6th is a tuning that can be played without using any pedals (look at Mick Hearn's videos). I strongly recommend playing around with it that way first until you can feel the intervals, then introducing a pedal to see what that does to what you've learned, then another - etc. until you're familiar enough to know, or "feel" what to expect when you engage a pedal or lever.
Anyway, however you go for it, thank goodness for new C6th players
