One of the most common ways to build a Solarian is to take Blitz Soldier 1 first, and one of the reasons for that is simply to let you avoid having Charisma set your Resolve Points. I think that's really unnecessary, in general (and that it's utterly bizarre that Solarians have any reliance on Charisma at all).
Use the rules below to change the Key Ability Modifier for various classes; go through each class and change specific Ability references to generic ones agnostic to the Key Ability Score for the class (such as the necessary score for a Mystic or Technomancy to learn or cast a spell). In all cases, set the score once and never let it be changed again, as Soldiers work now for Strength vs Dexterity.
Envoys:
You must choose an Ability used by one of your Skill Expertise skills. Add Life Science, Physical Science, Mysticism, Perception, and Survival to the Skill Expertise list. Life Science, Mysticism, and Physical Science can use the talent <Skill Name> Savant (As long as you have enough time, you can take 20 on <skill> checks to recall knowledge, even if you don’t have access to a computer terminal or other means of research.) Life Science and Mysticism can use the talent <Skill Name> Student (As long as you have enough time, you can take 20 on <skill> checks to identify, even if you don’t have access to a computer terminal or other means of research. If the thing being identified was created by a group or individual you are familiar with (normally including any major corporation or military), on a successful check you also identify what group created the thing identified.) Mysticism can use the talent <Skill Name> Adept (When you attempt a <skill> check to disable or repair, you can forgo rolling your expertise die to instead halve the time it takes to make the attempt.). All skills can use the talent Inspired <Skill Name> (When you attempt a <skill> check, you can choose not to roll your expertise die until later. After you determine what the check’s result would be, you can choose to either roll your expertise die and add it to the total or forgo the expertise die and reroll the check (see page 243). At 9th level, you can spend 1 Resolve Point to both reroll the check and add the result of your expertise die.)
Mechanics:
Dexterity, Intelligence, or Strength. An Exocortex can grant proficiency in Advanced Melee or Sniper weapons, rather than Longarms.
Mystics:
You must choose a mental Ability used by one of your Connection skills. A Charisma Mystic can learn spells from the Technomancer spell list.
Operatives:
You must choose an Ability you can use to pass a Trick Attack Skill Check (currently, this is Charisma, Dexterity, Intelligence, or Wisdom, depending on Specialization).
Solarians:
Constitution, Dexterity, or Strength. Add Perception, Piloting, and Profession to Photon Skills; add Acrobatics, Athletics, and Sleight of Hand to Graviton Skills.
Soldiers:
Constitution, Dexterity, or Strength.
Technomancer:
Charisma, Intelligence, or Wisdom. A Charisma Technomancer can learn spells from the Mystic Spell List, and may choose to have Techlore apply to any one Charisma skill and either Computers or Mysticism; once chosen, this choice may not be changed.
One of the most common ways to build a Solarian is to take Blitz Soldier 1 first, and one of the reasons for that is simply to let you avoid having Charisma set your Resolve Points. I think that's really unnecessary, in general (and that it's utterly bizarre that Solarians have any reliance on Charisma at all).
Monks and Rangers had Wisdom as their key ability score. Paladins had Charisma. It's not that bizarre that Solarians have Charisma. I think it's bizarre for the Solarian to choose Str or Dex when they are kind of Mystic Knights. Casting "Spells" and having an Energy weapon. It would kind of like having a Mechanics main attribute be Strength.
Going Soldier at lvl 1 is only thinking short game. Your DCs are Charisma based. Not putting into Charisma only hurts your powers.
Operatives:
You must choose an Ability you can use to pass a Trick Attack Skill Check (currently, this is Charisma, Dexterity, Intelligence, or Wisdom, depending on Specialization).
What? Do you mean, "You must choose the ability score that is associated with your trick attack."? If you are changing this you need to update the math. Notice how if the trick attack ability isn't dex you get a + 4 for balance reasons. Only one that doesn't is the Ghost but that is an error and one the devs confirmed it. Did you account for that math?
Mystics:
You must choose a mental Ability used by one of your Connection skills. A Charisma Mystic can learn spells from the Technomancer spell list.Technomancer:
Charisma, Intelligence, or Wisdom. A Charisma Technomancer can learn spells from the Mystic Spell List, and may choose to have Techlore apply to any one Charisma skill and either Computers or Mysticism; once chosen, this choice may not be changed.
So basically choose whatever ability or spell you want? Why not let the player choose whatever class feature they want too?