Umm. I can vaguely thing of a few scripts you can use that accomplish these goals but not a single script that does them all. If I were you, I would find a script for each thing separately.
I know there's a Digging script for VX you could rig to work with a chocobo.
I saw a timer script that can be utilized for racing the other day which you can use with a chocobo.
I haven't seen anything for farming, but you could probably event that.
The passability per chocobo might be the hard one. I think Modern Algebra has a script for determining and setting terrain tags for VX tiles. You could create several different events each one a different chocobo and use them like vehicles and restrict each event to certain terrain tags with that script. Etc. Think a little outside of the box. That should help.