e) Just have Tom Cavanagh play him.
I mean, how many characters has he played so far? (well, counting the seventeen Harrisons so far…)
f) “Ralph, why do you look so different now?”
“I took a long, hard look in the mirror, and I realized that my face was kinda douchey and I looked kinda racist. I figured, what the hell, I’m a shapeshifter, I can have whatever face I want.”
g) Becky?
Is The Flash the Arrowverse show that has kept the most (or maybe all) of its first season characters? It started with a Wells, Cisco, Caitlin, Barry, Joe and Iris, and they’re all still there.
Supergirl lost Winn, Cat, and James
Legends lost everyone but Sarah and Mick (and Gideon)
Arrow, I didn’t watch, but surely it lost a few first season characters over time.
Batwoman just lost Kate Kane (ouch!)
Not sure about Black Lightning.
The Flash lost Eddie Thawne. Of course, he was pretty much destined to die…
Also, technically, they did lose the Harrison Wells character, but the actor has stayed on the show.
I think everyone except Barry has also had an extended absence at one point or another, which probably has helped to keep the cast together (given the actors time for other projects and life events, and helped keep production costs down as their salaries have risen).
Technically the character wasn’t Harrison Wells but Eobard Thawne, who is a recurring character.
True. So, Tom Cavanagh playing Eobard Thawne pretending to be Harrison Wells was a series regular in the first season. Then, Matt Letscher playing Eobard Thawne became a recurring character. Then, Tom Cavanaugh playing Eobard Thawne who looks like Harrison Wells but isn’t pretending to be Harrison Wells became a recurring character. And Tom Cavanagh, playing various characters who look exactly like Harrison Wells but aren’t, has been a series regular the whole time. Or something like that.
Makes perfect comic book sense. 
Even if you count Eddie and EoWells, Flash has better retention than the other shows, I think.
Disappointing news about Ralph Dibney. Sure, they could recast him, but the actor was really good in the role and it just wouldn’t be the same having someone else play him with a new face. I’d rather they bring in a new character instead.