Starting on MicroZ
Two of the big considerations are adopting Microlite for my level-free experiment, and adopting it for my campaign world.
Stats was easy. I'm keeping the three used in the original Microlite design, Strength, Dexterity, and Mind. While I debated on the idea of combining Intelligence, Wisdom/Willpower, and Charisma into the Mind stat or not, I finally squashed my mechanics-hydra by rationalizing that specific aspects of mental abilities are also reflected in skills.
Speaking of skills, level-free construction and the voices in my head required me to beef up the 4 (or 5 for expert) skills used in Microlite. My skill list consists of Athletics, Discipline, Influence, Knowledge, Magic, Melee, Missile, Subterfuge, and Survival. While this may seem to be a bit much for a "micro" system, these skills also replace attack bonuses, caster levels, and armor class (more on that in a later post).
Each class has three class skills, which they start with 2 ranks each. Class skills are less expensive to advance than other skills, but there's no rule to keep a fighter from buying up ranks of Magic. It will be more expensive and he won't have a mage's special abilities for casting, but effectively multi-classing is a matter of investing skill points.
Advancement is easy now (compared to my 4E a la carte). You have class skills, other skills and stats.