Can't add anything about these two, but know of about a dozen places that do that. Southeast Asia, India, some in the EU even, Mexico, with of course everyone's "favorite". I won't linkspam to any of the places.
There's a number of places that do DM internships, some that do OWSI internships, a few that do both.
There are three ways these internships work:
1) Work-then-learn. Dressel. The big downside is that all you can do is unskilled labor, and they can fire you at will with no loss.
2) Work-and-learn. You do unskilled but DM-type work together with your course.
3) Learn-then-work. You do the course, then work it off. Working for real will earn you more than a course costs, but OTOH you get guaranteed opportunity to work it off.
All three of the above will usually still have you pay agency fees. Living expenses are on you too. Lots of monkey work, and really a job experience. Unless you can be very frugal, the living expenses can amount to a lot.
4) Not really an internship - expensive courses called "internships". Same as work-and-learn, except you pay for everything. In exchange, there's no monkey work (usually), they're between bare courses and real internships in length. Some can be started with fewer dives than agencies require. Also, it's a way to study above OWSI (in PADI).
Decide which kind(s) you're willing to go through.
All in all, if you have the money, you'll almost always be better off doing a regular course and working for some time. So if you have enough money to afford the expenses involved, you probably have enough to afford a course, if you shop around (not that I advocate for that).
Quality-wise, you'll get better experience traveling and diving than complimentary diving (on the same few sites!) included in the internship. You'll also get better job experience actually working as a dive pro than being an intern. But if you're critically short on experience, diving packaged in the internship can be a lot cheaper than fun diving.
So it's a way to get to instructor, if that's the goal. It's definitely not "the way". The way, if we're talking quality, is to work a proper job, study things useful in your diving non-career, like languages (Mandarin), seamanship, medicine, take long diving vacations in various places, and advance your diving skills. Procure a set of gear, get comfortable with it, get at least some technical training - it's very useful for improving your skills and approaches. Then, when you have everything, take the pro courses. This of course hinges on having a decent job that also allows for vacations.
Location matters, by the way. You have to be experienced and preferably get your pro training where you intend to work. Not necessarily right there, but at least in the ballpark - tropical and cold water diving are very different.
