Psionics System Design

(Before I start, yes I know Kwait_W made a Psionics Unleashed mod several years ago. Having looked at it, I think that Kwiat and I had different goals in mind with how a psionics system should function and feel.)

I am working on a points based Psionics system and I want some feedback on its actual design. I explicitly don't want to replicate how psionics is handled in 3.5 or Pathfinder, because I find it too powerful and because I don't think it sufficiently emphasizes the difference between psionics and magic.

Design
So far I have come up with the following fundamental design points:

1. Psionic abilities utilizes a point-based casting system.
   
2. Psionics is fundamentally different than magic.
   
3. Psionics abilities feel unique and thematic.
   

I think point 1 is pretty self-explanatory. You can use any combination of your psionic abilities until you run out of points for the day.

Point 2 addresses that psionic abilities are not subject to the same issues that magic has. Psionic abilities can be used when silenced, can function normally in dead and wild magic zones, ignore spell resistance, and cannot be dispelled using Dispel Magic. Psionic abilities that require a save would use save vs. wands. Psionic abilities can be used while wearing armor.

Point 3 addresses that psionics should be rare, and feel intentionally weird. Psionic powers are not just arcane spells renamed or prefixed with the word "Psionic"; they are completely different abilities with strange and powerful effects. Furthermore, psionic abilities should feel thematic; constructs, vermin, mindless undead, plants, and oozes can't be phased by being shown glimpses of their future (although they can be damaged if you use telekinesis to throw a large rock at them.)

Implementation
Lots of rambling about design ideals aside, I am unsure of how specifically I want to implement psionic powers. I have a points system that is working perfectly, as well as an otherwise unused kit flag that I can use to prevent psionic characters from using spells or items that would interfere improperly with their abilities.

There are a couple of different options for several steps of the implementation, and I'd like to get some feedback on which would be thematically acceptable while not being a PITA for users. For the purpose of this discussion, a "power" is a single ability (the equivalent of a spell), while a "discipline" is a group of powers (the thematic equivalent of a school, although most disciplines would only contain 3 to 5 powers).

Some of the decision points include:

1) Usability: Should powers only be usable once the psionicist has reached a specific level, or should a psionicist be able to use any power they know as long as they possess the enough points to pay for it?

2) Acquiring New Powers: Should powers be learned invidually (from a big list) or in groups (e.g. you pick a discipline and learn all of the powers associated with that discipline)?

3) Availability: Should you be able to use any power you know (like a Sorcerer), or should you select a subset of your known powers to use (like a Mage)?

Speaking personally, I think that, ideally, powers would be learned in groups, but you should be able to use any power that you know without having to choose specific ones. I think that not having a level requirement to use certain powers would also help subvert how magic is typically presented, but runs the risk of becoming overpowered if I am not careful with power design.

I'd also like to have Psions be able to dual and multiclass, so I'm eyeing either Mage (if using the spellbook interface) or Fighter (if using the innate menu) as the base class.

Does anyone have any thoughts or opinions on what I've brought up?