Shouldn't be possible. WhatsApp uses the phone number to sign in, and different SIM = different phone number.
I'm just tossing this out there, even though there's a big, fundamental difference. But it may help someone figure something out.
When I activated my WhatsApp account, my oft-cursed lack of a signal in my house prevented me from receiving the activation code via text. But! I provided my
landline number, the code was spoken to me via a voice call, I activated WA, and that was that.
Until I bought a new smartphone and tried setting up WA on it.
By then, I had
long forgotten any of that. I
knew WA was backing up every night--I could *see* its file online, for heaven's sake! The file's name--the part of the name I could see in portrait on my phone--certainly looked right. I tried all sorts of things, to no avail, as I tried to get WA working on my new phone.
Oh, did I mention that the new phone
did get a signal in my house? Not much, but good enough to momentarily connect to activate the account. Which kept failing... I'd try restoring its backup, it would say it didn't exist, and I'd cuss out loud "what the *%@)&! do you mean it doesn't exist? I'm LOOKING RIGHT AT IT!"
Then I thought, hmmm...I wonder what that backup file's name looks like in its entirety...

...switched to landscape... OMFG! It's my
landline's phone number! At first I was just baffled: why the hell did I use
that?! Then it all came flooding back...
So the moral of the story is, well, I'm not really sure!

But I do know that one WA account can have two phone numbers associated with it. And you can use a landline number to register.