I think the main gripe about Devlin Stone was he popped up fully formed, from nowhere, to lead a coalition that was unbelievable at best dealing massive defeats to an enemy that should've beaten them to set up an empire that everyone suddenly said "yeah... cool .... have all these worlds and units and stuff", with no basis in the BTU. That wasn't the Republic at fault, or Devlin Stone. It was the way in which it was handled under different owners that rankled - not to mention the Dark Age and ClickyTech which didnt sit well with the fandom.
Have consistent characters that have some basis in reality and fans will be happy with that. Dont have someone suddenly go all mustache twirling for no good reason (ie mad/bad/dangerous to know) and dont have unreasonable plot armour.
Baddies dont need to be bad. The best baddies you can empathise with, have some understanding of how they got there and made those choices. Baddies who show up acting like a 2 dimensional Bond villain should get little traction.
THIS? ^ what phoenixalpha said? THIS is exactly it, including the reason most of us who didn't like the Impossible Devlin Stone and his Superfriends felt the way we did. The aftermath/past-tense massaging that is the Jihad books, barely spackles over the gaps-and only if you stand back a few miles.
Basically hitting EVERY wrong note for a 'Chosen one' storyline. Including, but not limited to, the moustache-twirler Bond-Villain Badguy, leaders and whole factions playing directly against their prior history, literally impossible victories...or at least, so improbable that the vegas odds would be on the side of 'inside job'.
Unlike Tassa Kay's suggestion, this is NOT what we're asking for...or suggesting, or speculating on.
If you're going to have a 'Bond Villain' baddie (and let's face it, Battletech is chock full of them whenever there needs to be a major storyline push), at least make them interesting, clever, and not stupid or utterly batshit.
I know, 'But Batshit's easier than working out someone intelligent who actually
has a ****** plan that doesn't involve suicide by nuke, weird replacement rituals that wouldn't pass a job interviewer, kinslaying insanity, suicidal policy (disarming your line units in the face of an invasion? really Katherine?), you know, a villain that makes the heroes look good because he (or she) is
genuinely hard to defeat rather than having a massive, obvious, suicide-pill flaw like madness or stupidity (Malvina, Mad Max, The Master, Brett Andrews, Leo Showers or Lincoln Osis...)
The next Bigbad needs to be challenging, not because they're Reckless or Destructive, but because they're smart and effective, and completely at odds with the ambitions of the Designated Protagonist...with enough story they could BE the Protagonist in a close parallel timeline.
That means stepping out of the shadow of "we'll default to giving them mental illness, insane evil, suicidal stupidity, or an irrational blind spot"
I want a bigbad that could be the HERO if they weren't on the other side, get it? Instead of temporarily dumbing everyone down to make them (or the Hero) look brilliant for doing the obvious things, actually invest the time and effort to write the 'evil genius' as if they were, themselves,
intelligent adversaries, who do not suffer from crippling mental illnesses. Give'm a plan that's actually smart, give them subordinates that aren't two brain cells short of a lobotomy.
Make it so when I open the Novel, or the sourcebook, I can't ascertain who's going to win in the first five pages. Gimme DOUBT, make the tension have TENSION. When the Heroes get their big drama moment,
actually make it dramatic because they actually feel like they can LOSE.
You feel me?