If you skip critical for playthrough swimsuits, you can get every candidate in first game.
Proof in attach.

Interesting, can you tell more about those swimsuits, and how can you skip them?

Also as I see MB is used to fill shops with more stuff (by Item plans), so it means having to forget that shops exist on 1st cycle?

Swimsuits are unlockable with plans equipment. You would get them in 7-8 chapter.
"Skipping" them is a joke on choosing swimsuits over character.
You get 3300+ MB, that's enough to unlock candidates, mandatory dungeons and harder enemies for them (For example, without Tougher enemies in Neo-Geofront you can't get drop for Nepgear)and still have leftovers.
I have 99MB unspent(after filling shop with healing items and additional armor/weapon),

If I didn't want to finish game ASAP until Fallout 4, I would've picked this instead of one of the chars:
Colosseum(512 MB). It adds good farming spot, good equipment, useful quests.
Super EXE drive (256) - faster fill of EXE bar
Break damage limit (256) - 9999 max damage per hit by default. Only main char ignores that rule, other chars need either jewellery or disks.

Sacrificing Colosseum and Break Damage Limit is a bit too much for me, I think I will skip some of those additional characters in 1st playthrough. And knowing IF games, I don't want to hold myself from filling shops with relevant gear.

I'm not insisting, but break damage limit isn't a big deal - you get good ring with this property for one character, Nep-nep ignores it and Nepgear gives that property when in back row.
But Colosseum seems worth it.

As I said, it's a joke about priorities :)
Realistically, unlocking all characters in first game would block for first game:
Colosseum - very good source of exp, money, items, easy way to change shares.
Most side dungeons - again, quests, items, share changes...
Quality of life plans - increased Exp, money, droprate, super exe drive...
For one city I had only one quest to improve shares by 1%, needed to do it 14 times :)

After having every character, I would recommend to unlock only Uni in first game, she has an amazing farming skill.
Second priority I would give to twins - one is a healer, good to replace non-CPU Compa.

I see... To CPU Candidates transit to next playthroughts?

Yes you get them right away too, unlike the other CPUs and makers.

Yes, they do.
More so,
Spoiler about true ending
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*SPOILER*
They even fight with you in last battle during True ending fight, when other characters leave you alone.
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Better hide it, though, someone could accidentally read it. Like I did. :D Although it's kinda important... it would be kinda impornant, because that a good reason to do true end later, unless it's 'easy mode' when you get there.

The true end isn't really anymore challenging than the normal one, especially if you are already on NG+. It's just a 1v1 boss fight, instead of the usual 3v1. Just Buff->Rush->Exe->Repeat.

Well, if you say so... :)

I just quickly replayed. The last fight has way less hp than the normal last boss but is a 1v1.
I needed 3 complete turns of my lv999 party using power attacks to kill the normal end boss while the true end boss needed only a single combo. So if you managed to kill the normal boss before, the true end one will die pretty fast.

The CPU candidates only join you in that last fight if they were in the active team or the backrow. Otherwise you'll still be alone.

Thanks, but you rised another question... uh... how long last boss fight takes if you play your first playthrough? How much you had to grind, then? Because this "3 turns of power attacks from 999 lvl characters' looks preatty menacing. :D