One question to ask yourself is what you want to do after the PhD. Do you want to go into Academia as Professor/ML Researcher? Or do you want to work for a big company doing ML Research? If it's a big company, are are you thinking Google/Facebook or a company that does ML research, but is less well known?
If you want to become an Academic at an R1 university, I would really recommend not taking any shortcuts. Your career success depends on your research, and your research depends on your professors and the people you work with. Going to a 2nd or 3rd tier PhD isn't worth it if you want to become an academic focused on research.
Figure out how you can get a master's from a a good program. From there get a PhD from a good school. Avoid the tier 3 schools which offer transitional MS programs for people with non CS backgrounds, but it's really a watered down MS. I'd say the same is probably true if you want to work for Facebook/Google Research.
There are companies that do ML/AI research, but they are not really commonly known. One way to find these companies would be to look at the Sponsors for conferences (e.g. NeurIPS 2019) and look at the names. These companies would probably be more open to somebody who didn't do a PhD at the top 10 R1 schools.
I don't remember which schools off the top of my head, but some schools have take an intensive "pre-MS" year before your Master's. This is for people with non CS backgrounds, or CS people who are coming back to school after a long time.
Don't waste your time and money getting a PhD from an unknown school if you seriously want to go into research in any shape or form.