I'd like to see a setup for Creative Mode that allows you to unlock abilities on all classes.

The /aim command is designed for ability data editing, just use /aim help to see more info. For example, /aim learn_all unlocks all skills under current category.

Let me rephrase. I wanted to be able to use all the abilities for all the classes, instead of being limited to one class, while in Creative Mode as an OP.

I see. I personally don't like this idea because it complicates things (the current framework is based on the assumption that one player holds one category at any time, and why would player be able to access all skills because he/she is admin?).

IMO you can use command to simulate what you want currently. There is something I can do to simplify the process (e.g. make all skills unlocked by default while in creative), but unlikely would I support using all skills.

In future there will be some rework in base API, that might allow 'mixin' of different categories' skills. When that starts I'll reconsider it.