I gag at the mention of similar skills.
I play RM2/C and really dislike the category system, so I'm always observing your threads on removing it. . .but even I have to admit that unrestrained similar skills is FAR FAR worse.
Then again, varied difficulty always did seem to work.
Like if looking for this herb in the woods the skills Perception or Foraging or Herbalism or Lore: Herbs might apply. . . just at different difficulty levels.
Similarity, and categories, always struck me as attempts to deal with the above, that RM does well, and the below, that RM does poorly:
If you have Perception, Foraging, Herbalism AND Lore: Herbs and all skills apply to the task do the bonuses in any way combine or stack?
The category bonus does a decent job of covering the part of the skill that would overlap between them, but I wish there was some logical means of using two or more skills at the same time when it made sense, rather than creating an artificial meta category bonus. (especially if the two skills you want to use together lie in different categories.)
i.e. if you have 20 ranks of foraging, and 20 ranks of Herbalism, that should make foraging for herbs easier, or allow some sort of cross bonus. . .but neither system allows for it that I know of. This gets especially hard with two utterly varied skills in different categories that use different stats.