the problem of course is that it has to remember what number it used, which is incredibly hard to evolve.
I would recommend restructuring the sysvars such that they all work independantly. I don't have a concrete proposal yet, but it would probably be something along the lines of what I propsed earier, with all tie functions pre-pointing at an existing tie.
Then all you have to do is evolve, in this order:
feed through tie
create tie
Instead of:
feed through Xth tie
set tie fxns to X
fire tie X.