Ihave been using the Maco/Compard C-41 kit a lot. The best feature of it is, like robert/fotohuis said, is the possibility to replinsh it. The Bleach, which is the most expensive component, can be replinshed by "areating" it and also adding undiluted bleach to compensate the diluting of water carryover. The fix is basically B&W fix and normal hardening fix can be used. The developer is in three components in the Compard kit and the ageing process starts just after you mix the three developer components. When kept separate, the Digibase Compard C-41 developer components have an infinite lifespan.
When doing custom processing like "cross process" you have to extend the bleach and fix steps by 2x or 3x due to the large amount of silver in the positive color film stock. If you extend the developing time, you greatly increase the grain and contrast. I sugest you leave the color and contrast tweaking to photoshop done after you have scanned the negatives. The problem you were talking about, are dealt in detail when you google the phenomenon "Leuco Cyan Problem" It is the insufficent bleach step which results in silver still in the emulsion, that starts to darken and also eats up the color of the negative.