I would def hire an H1B even it costs me upfront premium for those reasons.
No they cannot, this causes issues with their perm processing. You need to find an employer that can sponser your greencard otherwise you are out of country in 6 yrs. So you not just have find an employer that will transfer your h1b but also pick up perm processing from your previous employer.
More info here,
https://www.murthy.com/2019/12/26/how-a-job-changes-may-impa...
This is just one example.
It is far far far away from 'freely'. Given the arbitrary nature of uscis processing people try to minimize their iteraction with the agency. No visa employee will attempt this risky move for a 10k salary bump.
2. Yes FAANG's might be ethical h1b users that pay 300k+ but that doesn't automatically imply everyone else is.
3. I have personal experience with this have encountered higher manager wanting to hire h1b for the reasons i've described above.
4. X is conspiracy theory because there are exceptions to X is a basic logic fail. 'real conspiracy' is an oxymoron.