I'm of the opinion that psionics should be organized in a more...pseudo-scientific manner.
That is, spells, even with the cleanup brought by 5e, remain kinda all over the place. Some things are assigned to schools that don't really make any sense (e.g. why on earth is pass without trace an Abjuration spell?? It's literally concealing! It even uses the words "concealing aura"! It should absolutely be an Illusion!)
With psionics, since we're starting from scratch, we can organize things into cleaner, more focused (& better-balanced...), more categorically cohesive groupings. Further, because psionics generally has involved the use of "power points" in various ways, we can build from that baseline to create something that works fundamentally differently from spells.
So, from the jump, I would want to either (a) define all the categories of psionic stuff I want psions to do and then invent an adequate number of powers to fill those categories, or (b) set out a bunch of powers I'd want psions to have access to and then organize those into discipline categories that have a clear, logical arrangement.
Just doing one of those two things would instantly make psionics and spellcasting distinctly different from one another--but I'd like to go a step further. We've seen some things that suggest the idea that some supernatural power doesn't work the way spells do, where a spell is a discrete mechanical package which might be able to do the exact same effect but more strongly, or more widely (e.g. affecting more targets), or for a longer duration, if you power it with more mojo. Instead, there are gentle suggestions here and there that some supernatural effects are more like they have a core baseline A, and then as you get stronger you gain the option of B (but it costs more resources), and later the option of C--where A, B, and C are all related but separate effects.
That's what I would want to see psionics do. So, for example, you could have under the Kinesis discipline the Cryokinesis talent. By knowing Cryokinesis, you start off with (say) a Frost Shield power that gives THP based on how many PP you sink into it (but those THP take double damage from fire--not your actual HP, just the THP provided by Frost Shield). Then when you reach a new tier of powers, the very fact that you know Cryokinesis unlocks a new power, say Stalagm-Ice, which allows you to manifest spears of icy cold from the ground. Two different powers, same talent.
By doing this, Psions are forced to make tough choices. They have to invest into only a limited set of talents, but each talent provides a mix of offense, defense, and utility, depending on the theme and flavor of the talent. Then, subclasses can be designed which offer inbuilt elements, and possibly favor or support specific playstyles, e.g. a "Psychokineticist" subclass might need 1 less PP (to a minimum of 1) for using any power belonging to the Kinesis discipline. Psionics then becomes extremely diverse, but inherently bounded--no Psion can do EVERYTHING, but Psions collectively can do almost anything. This creates a structure that is much easier to balance than the "I learn ALL THE SPELLS" of the Wizard, and yet still quite open and supportive of player choice and style.