In order to implement alternative skill systems such as presented by Pathfinder Unchained, it becomes necessary to hide skills that should not be used in a new system.
As an example, in the consolidated skill system Climb and Swim are merged into a new Skill Athletics. My suggestion to implement this in a way that not every ability or item providing a bonus to one of these skills or that uses them as a prerequisite need be recoded is as follows:
1) Hide Climb and Swim with VISIBLE:NO from both the interface and the output sheets. Remove these skills as class skills from all classes where appropriate.
Climb.MOD <tab> VISIBLE:NO
2) Define a new skill Athletics. Add this as class skill where appropriate.
3) Transfer skill ranks from Athletics to Climb and Swim, so prerequisites that require a certain number of ranks in one of these skill are maintained if there are an appropriate number of ranks assigned to acrobatics:
Climb.MOD <tab> BONUS:SKILLRANK|Climb|skillinfo("TOTALRANK", "Athletics")
4) Transfer miscellaneous bonuses applied to Climb or Swim to Athletics.
Climb.MOD <tab> BONUS:SKILL|Athletics|skillinfo("MISC", "Climb")
In this way, no objects using Climb or Swim should need to be modified, and all functionality is transparently transferred to the new Athletics skill.
The one thing standing in the way is that VISIBLE:NO is not allowed for skill objects. Is there any reason that would prevent this simple change?
Is it possible to use VISIBLE with PRExxx in order to check a variable that controls whether or not the alternative rule system is enabled?
I might be missing something here.
You've hidden Climb and Swim with a .MOD and removed them as class skills. What if I'm not using this sub-system? Surely your .MODs have removed the skills that I want? how do you make it conditional when these .MODs happen at source load. They are not dynamic, you have them or you don't.
Well of course this should not apply when you don't want to use that subsystem. It's not a global change. Whether this will be done via PRExxx tags or individual PCCs for each subsystem remains to be seen.