Others have detailed the reason why building your own SW station is not cost effective. I'll detail two subjects I think you don't understand well.
6. As to some 'end times' beliefs outside the US, I don't know about central/south America, but I know at least some places in Africa have similar beliefs and interests. I think in some of the nations those that do believe keep very low key. I will continue to study that.
What places in Africa?
There are over 50 countries. They range from the predominantly Muslim Arab nations of Northern Africa where Arabic is the dominant tongue but with a number of regional subsets. Sub-Saharan Africa has over 1200 languages and dialects, with the lingua franca for many being Swahili.
Only a few countries have English as a primary language. In the rest, any English speakers will be the very upper income and social levels. Is that your target?
7. You're correct in that I do assume much of the world speaks English as their 2nd language. I've been taught that English and Spanish are the 2 predominant languages out there. English and Spanish are what I envision the programming to be in, at least initially.
No, only around 20% of the world's population knows some English. Only about 600 million, less than 10%, have it as their first language. Those that know English as a second language in their vast majority don't use it for anything but work and their profession. They don't generally spend a lot of time looking for short wave stations in a language which is not their primary tongue.
Example: the person in Puerto Rico who works at a stock broker / investment adviser firm. They have to use English for most investment transactions and paperwork, but will talk to customers in Spanish. And when they get home, they will watch Spanish language TV and speak Spanish to the family. English is "work" and takes effort to use. It is less comfortable.
Similarly, the engineer in Ghana who works with a multi-national natural resource company may deal with co-workers from a variety of nations, but they use English as a common language to do business. But that engineer, who may be from India or Germany or Egypt or Japan or.... is going to go home and watch some videos or talk with their family in their native language, not English.
And none of those people are looking for new and interesting things on shortwave. If they are out to explore and satisfy curiosities, they are on the Internet.
When this subject came up, I asked my daughter in Ecuador to check the electronics stores next time she went to her favorite shopping mall. She could not find a single shortwave radio in any of the three stores she went in to ask. Two did not even know what she was talking about!