First: Most point-buy systems are pretty limiting, too. Powers and abilities tend to increase in smaller increments in point-buy systems, unless you're talking about very coarse granularity point-buy systems (everything costs 1 point.) Most of your character improvements are a +1 to one narrow skill; if you want a bigger jump or a much grander power, you have to wait longer. Even in a somewhat coarse point-buy system, such as the way characters gain feats in D&D 3.x, you often have "prerequisite trees" which slow down advancement.
Second: The limitations that were specifically being cited in this discussion weren't skill or feat selection, but were race/class restrictions: minimum ability scores, level limits, and forbidden race/class combos. But these limitations are pretty easy to fix without switching to a point-buy system: ignore them. It's not without precedent.
In fact, you actually have three options when it comes to these areas:
- limitless: no minimum or maximum, no forbidden combos.
- hard limits: some combos are flatly forbidden, minimums and maximums can't be exceeded.
- soft limits: minimums, maximums, and restrictions can be altered by other character details. Soft limits can range from semi-hard (restrictions vary from character to character) to semi-limitless (no prohibition, but a penalty applies if limits are exceeded.)
It's trivial to change the limits in D&D, but doing so changes the feel of the setting. Because it's so trivial, Liber Zero will stick to the original limits: semi-limitless for ability score minimums, hard limits for race/class combos and level limits. There will be notes that you can ignore level limits or change them to semi-limitless (xp penalty after reaching level,) but new races should be designed as if they have hard limits.