I've thinking about things a little, for a way for my groups use of skills in C&C to 'fit' a little better with the Siege Engine System - so we can actually use both approaches, allowing characters to attempt pretty much anything whilst maintaining a more structured approach - with appropriate Challenge Ratings of course.
This would still allow (for example) a Fighter to attempt to pick a lock - he just won't have much of a chance of succeeding.
Rather than have a long static list of skills, the players should choose skills that fit their character concept and (with the help of their Castle Keeper/Dungeon Master) come up with their own list of skills and their descriptions.
Skills would still (sort of) have levels – and these levels are ‘rated’ like any characters attributes - Tertiary (the lowest skill level), Secondary (average skill level), and Primary (the highest skill level).
Like class skills, the character applies any appropriate attribute bonus to the task at hand -strength when shoeing a horse, or dex when making a horse-shoe – both would be considered to come under the skill heading of blacksmithing, but you would require strength for one and manual dexterity for the other. But unlike class skills, you don't add your class level in a 'straight' manner.
Primary skills get a +1 bonus per level, Secondary gets +1/2 levels, and Tertiary gets a +1 bonus per 3 levels.
Your base challenge rating is determined by skill 'level' – level 3/Primary = 12, level 2/Secondary = 15, and level 1/Tertiary = 12.
The Number of slots a Character has for his Secondary Skills are equal to the Characters (INT+WIS), + Characters Starting Age/10 (another advantage for most Non-Humans).
What levels your skills start at is dependent upon how many skill points you have, and how you spend them.
Level = Cost
1/Tertiary = 1 point
2/Secondary = 3 points
3/Primary = 6 points
For example, Brother Kydric has 26 ‘Slots’ to spend on his Secondary Skills – and he decides to spend 6 Slots on Healing. Giving him the Healing secondary skill at Level 3/Primary, his base challenge difficulty for all tests involving his Healing secondary skill is set at 12.
A Character gains Secondary Skill points at every ‘Odd’ level (3rd, 5th, 7th and so on), the points he gains are equal to his Int or Wis attribute modifier (whichever is higher) +1 (with a minimum of 1).
To make the check, the character performing the skill simply rolls a d20 and adds his appropriate modifiers - the difficulty is set by his skill level (either 12, 15, or 18) plus any challenge rating added by his CK/DM.
So if a character is level three, has a dexterity of 15 (the appropriate attribute in this example), and his skill level is 3/Primary – when using the Weapon Smith secondary skill they are allowed a +4 to their roll.
In some instances the use of skills causes another to make a saving throw. In this case, the character, monster or non-player character makes a saving throw but modifies the roll by a -1 for each level of skill the character has. This is also adjusted further for any attribute modifiers. When a saving throw is called for, the character’s level or monsters hit dice also affect the roll.
Furthermore, there are always circumstances than need some modification beyond that mentioned above.
Unusual circumstances, the weather and pure chance can come into play to effect the chances of success. In addition, the difficulty of the situation adjusts the roll.