I could see Devito as Louie from Taxi killing with no mercy.
“You Sarah Conner? Too bad because you have nice knockers.”
Bang bang!
"Please vote to preserve the unique character of Warren…" - Robert Duvall

1. Because having Danny Devito going around killing Sarah Connors would be unintentionally laughable.
2. Arnold was originally interested in Reese with Lance Henrisken envisioned for terminator. But to have Arnold in the movie and NOT play the terminator when he has a naturally robotic voice and accent, a naturally wooden and expressionless acting style, an otherworldly body, and a face shape that looks like the skull of the endoskeleton, would be a missed opportunity to say the least. For a film with limited budget, the plausibility pays for itself.
3. They went for infiltration with the T-1000, but even he was slim and agile and fit. Designing the skin if the machines to look like Americans with cholesterol problems would be silly. The T-800 was a bulkier model so it’d make sense a tall muscular skin would fit over it. It works and Arnold’s perfect for it.
4. Arnold still passes as human, and bleeds, so the infiltration concept still works.
5. When people have realistic human-looking sex dolls, they go for perfection. They don’t want to have a sex doll with fake pimples and varicose veins designed on it so it looks more “human.” Humans like attractive.
   Never lose your desire.

For us the movie audience.
Did you know that OJ Simpson was considered for the role?
That would have been something as him being a murder machine in the first one then come back as the machine hero in the second then get accused of murders?
You bring up an interesting point in the OP.
Yeah, why not have him blend in more looking like an everyday person.
I think we got that in T2 and 3.
What do you think of those Terms?
Fit the bill?
"Please vote to preserve the unique character of Warren…" - Robert Duvall

Why should an infiltration unit be intimidating in any way whatsoever?

They're designed to be infiltration units, yes, but they're not ONLY designed for that. Their human skin is also designed to look like a intimidating human soldier with muscle mass.
The idea is to intimidate people with the skin alone so that he doesn't have to reveal his endoskeleton.
Also, if a terminator is sent back in time, how many people are going to a think a well-built dude is an android? The fact he sweats, breaths, and bleeds is enough to pass as human.
Never lose your desire.

One that looks like Fagazi,woman's panties included.
Ho Ho Ho

"They should design a terminator that looked like Rodney Dangerfield…"
Yeah, and he would kill us with laughter and really be a danger field!
On the other hand, he would just bitch and moan all the time about not getting the respect that other models get.
"Please vote to preserve the unique character of Warren…" - Robert Duvall

"Arnold Schwarzenegger miscast as the Terminator"
——————————–
Honestly, I don't think anybody could have played the role better than Arnold Schwarzenegger.

"Arnold Schwarzenegger miscast as the Terminator"
——————————–
No, That is Most Definitely a "No".
He was without question the Number 1 Best Choice to play the role.

Just with the technologically capable of making a terminator with organic skin that bleeds and sweats is enough to pass as human - they don't need to make short and overweight to do this.
But that's the whole point - if the purpose is to infiltrate, then yes, that is precisely what they would need to do.
As for looking intimidating, to what end? Animals evolve to intimidate so they won't have to fight - far better to frighten off rivals and predators. But terminators are pure hunters, and scaring humans into running away would be counter-productive to what they were aiming to achieve. They want to flush the humans out, not make them hide.
The only reason terminators look menacing is because it makes for a more menacing movie. Not because it'd make sense from a practical point of view, because it wouldn't.

Yes, and no. But more, no.
The endoskeletons themselves were created to defend Skynet in the future: they were designed to look buff and intimidating. They wouldn't create short, fat endoskeletons as fighting soldiers. So any human skin you put over the endoskeleton is naturally going to have a build and facial structure similar to Arnold.
Just with the technologically capable of making a terminator with organic skin that bleeds and sweats is enough to pass as human - they don't need to make short and overweight to do this.
They did do your assessment to the T-1000. Robert Patrick was looked more like an average Joe to blend in with society, but could be intimidating as well. But they're going to go as far to make the terminators comical to look at. They wouldn't even do that in real life.
Never lose your desire.

I think the Austrian accent helped a lot beyond the basic premise of the story.
Ding Dong
!

They also at one point BEFORE Arnie got the role wanted future DOUBLE-MURDERING OJ for the role.
Yes, but they decided no-one would find Simpson believable as a cold blooded killer.

Lance is a character actor.
Makes me wonder if that would have gotten him bigger roles should he have been the Term.
He did get to play a robot in the JC movie of Aliens instead, which is interesting and that robot seemed to be a better fit for him.
"Please vote to preserve the unique character of Warren…" - Robert Duvall

Lance Henriksen
was ORIGINALLY supposed to be
The TERMINATOR
. They also at one point BEFORE
Arnie
got the role wanted future DOUBLE-MURDERING
OJ
for the role.
“Call a SPADE, a SPADE; and a TRANNY, a TRANNY, or an IT!!!”.
"THAT'S SOME BAD
SHIT
,
HARRY
!".

I totally agree with Karl, but Arnold does have that robotic-type voice that is perfect for the role.
He just really looks and acts like a robot throughout the film. I never thought of him as much of an actor, but you gotta admit–He really nailed the part!

But it would be very hilarious.

This message has been deleted.

Yes, that much is true.

I don't disagree. My thread here isn't really serious. Even though it is on point.

Technically, yes. But no.
We got an iconic and memorable performance out of Schwarzenegger. One that worked perfectly during the era of the 80s. Most movies from that time are cheesy and you have to suspend disbelief. It probably would have been a fairly forgettable movie without him.