Anything can work with C&C, just depends on how you want to do it.
Like how I do feats from 3E. I don't do feats, per se, I just allow anyone to do a SIEGE check to attempt any Feat like action they can think of.
Skills, I went with a "Everyone has 10 skills, but if you take a class skill you treat it as TN 18, then add level and modifiers." I too got rid of ranks and just went by level and attributes. The +6 from being Prime versus non Prime was plenty of variation for skills.
As for 4E, I liked the mages ability to cast spells all day long, so the way I am adapting it to C&C is as follows:
SPELL CASTERS:
A new class ability for ALL spell casters, except Paladins.
Divine/Arcane blasts. These are a pure energy attack that any spell caster can use every other round as long as they do not cast any spells on the round in between. Yes, this means all day long. This is because that round is a recharge/gather the power round. This attack requires a "To hit" roll versus the targets AC, but the casters BtH for purposes of this attack is equal to their level and its modified by their DEX. Damage is 1d4 per level of the caster and requires a "item" as the component for this ability. It costs 20 GP per dice of damage. Typically a cleric uses their Holy Symbol and Arcane Casters most frequently make a wand.
As usual, I do allow a SIEGE check to cast this every round, it will be CON based, and failed checks will cost a temporary loss of one CON point to simulate the exhaustive nature of wasting the energy as well as gathering it so quickly. The CL will equal the amount of dice you want to do for damage, and the base TN will always be 12, since this is now a "Class Ability" for all spell casters.
So C&C can have anything used with it, but I am enjoying turning it into the SIEGE system rather than porting the whole idea over as is.