I'm playing a psion egoist created in 2e.
In 2e he was dual-class (4F/7Ps by the time we finally decided to go to pathfinder - we're adults with kids, we game like once or twice a year, so we just kept playing 2e since we had the books up until a year ago).
An 11th level character in PF is very different from a 4/7 in 2e. Converting required a lot of caution. But we ultimately did it.
PF has different rules, and it's not min-maxing to say that a character would make different choices in a world with different rules. I looked a lot at the problems of shorting yourself a level or four and decided to go with the PF option for retraining levels. So I used a bunch of down time to retrain 2 fighter levels into psion levels. But he's a melee character and I didn't want to get rid of his essential nature. So I thought about leaving him there. What I ended up hitting on was the use of psionic knack. I needed it if I was going to give him fighter levels, but then I read the rules and found Bonus Power Points are calculated based on your manifester level.
So if you take one level of something else to get access to martial weapons and then go all metamorphic, what better way to do it than take 1 level of Psychic Warrior and gain a lot more Bonus Power Points than you would otherwise have…and which mix seamlessly into your Egoist power pool?
Moreover, you're talking about getting access to other magic items: Remember the amazing versatility of Psicrowns, but they don't allow you to use a spell in a psicrown unless it's on your class list. With a level of Psychic Warrior you get psi-crown access to all those awesome spells you would otherwise be denied. Really, this is nothing but win.
Sorcerer progression in spell level, but full manifester level (psionic knack). You're behind in PowerPoints at mid-levels, but at early levels you're actually ahead b/c you get bonus power points twice and for more levels than you actually earned.
With complete psionic-magic transparency, Eldritch Knight becomes a possible prestige class. But don't take it until you get either the Egoist 8th level power or the Transmogrifist 8th level power.
At that point, you're 1PW, 8PS, 1EK, but your manifester level is 3 for PW and 10 for EK. If you have an Ioun Stone, it's 4 for PW and 10 for EK. Since your stats should be pretty boosted by now, you'll have 4 times the bonus Power Points for PW to help your Psion levels through. At the same time you have BAB+6. This is actually the low point for the character, and at 19th level you have 17 levels worth of psion manifesting ability and PPs, a 15 BAB, and your stats are seriously maxed. You have access to 9th level powers. And you have 1 level to decide whether you might want to play at Epic. If you do, take a class that gives you one more BAB to get that 4th attack. If you don't your 18th level of psion ability looks good to close out the character with a bigger boost to PPs than you'll otherwise get, plus a little more variety in 9th level powers.
If EK isn't available, there's Metamorph. It's not as good, but gives a boost in HP and BAB over the default.
You'll only get 3 attacks, not 4, going the metamorphic route, but what seems like a disadvantage is PPs is totes not: you have permanent metamorphic powers! It's this scenario that makes the Transmogrifist option shine: with +50% to all numeric values (not just variable numeric values) your permanent +6 to Str, Dex, and Con from maxing out The "Abilities C" menu becomes a permanent +9 to Str, Dex, and Con. Sell all your physical stat boosting items. You don't need them and can put a huge amount of money somewhere else. Plus, you get +3 more enhancement than you could get any other way.
It not only creates a great melee combatant, but there are awesome power/magic combos left to you. Particularly with size boost + a d10 or d12 weapon that has the impact feature, increasing damage to that it would have if it was 1 size bigger. It's not worth a +2 bonus to your weapon normally (just adds a d6 damage, no bonus to hit) and if you increase in size to L, the weapon goes from 2d8 (for a weapon originally doing d10) or 3d6 (for d12 weapons) to 4d6. That's an increase of a d8 for the Bastard Sword and other d10 weapons. But it's an increase of d6 still for the d12 weapons.
Ah, but if you start with an M size 2 hand weapon that does d10 or d12, you do 2d8 or 3d6 not size changed, but 6d6 size changed twice.
But wait, that's not all: the transmogrifist gets +50% to all numerical values. That 2 size changes on ability list B? Well it's 3 size changes now! I don't remember if weapon damage goes from 6d6 to 8d6 or to 9d6, but either way that +2d6 or +3d6 makes a huge difference…especially when it's one of the few damage types that can be multiplied on a critical hit. Totally worth the +2 on the weapon.
But wait: it gets better still. The "psychic" weapon option gives the weapon a variable enhancement bonus based on how many PPs you have. You only need 30 to get +3, so at character level 7 or 8 you'll be spending most of your time with a +3 weapon, and almost all of the rest with a +2 weapon. These are really built with Psychic Warrior's PP progression in mind, b/c no one thinks of psions as a melee class. So as a high level character, you'll almost always have a +4 or +5 weapon on hand (especially if you use rotating, low-cost psicrowns for all the Psychic Warrior buffs). But the cost for the Psychic Weapon feature is a flat rate about the same as a +3 weapon. It's a bit hefty early on, but the special features you add later (keen, etc.) are all cheaper than they would otherwise be because for your +4 or 5 enhancement bonus at 12-13 level, you only enhanced the weapon to +1 (so it would take the "psychic" option). With 3 levels of weapon features, you would pay for a +7 to +8 weapon (100 to 125k). But the Psychic weapon gives you those weapon features for 64k + the 35k flat rate. It's the same as a +4 enhancement bonus. It has the risk of going down to +3 territory sometimes (even +2 on rare occasions, but you have to be below 5 PPs to get to +1, so that's should be pretty well rare in a high level character).
But of course, you also get the +5 bonus much sooner than you would probably otherwise pay for it, and as you add further enhancements, the cost comparison only gets better. Add in the savings on physical stat enhancement, and the transmogrifist metamorth with permanent changes to other abilities (like size) and you come out a combat monster, though with a few less BAB and one less attack than a 20th level fighter or the Eldritch Knight + 2 levels of PW (1 at first, 1 at 20th) option. Of course, Eldritch knight can't give you permanent stat changes and the 20th level fighter is just a fighter…and there are lots of magic items to purchase with the money you save on your weapon and stats.
Really, it's a fun option. You get 9th level spells either way (though the metamorph route doesn't get them until 20th level). And your manifester level still rocks with the psionic knack trait and maybe an ioun stone.
What more could a buff-lover want?