There really is only two results of letting in expats.
1. They will bring their money into Thailand and invest.
2. They will bring their money into Thailand and spend.
Rich people are rich because they know how to invest. They invest in Thailand because Thailand is a good investment. That has to do with the business environment, how well the economy is managed and laws concerning investment. It has nothing to do with visa's for living in Thailand. The rich may get a visa, but they are not going to invest because they have a visa. They will spend, but there are few of them.
Regular retirees, will also not invest. They can't afford it. But they will buy a house, they will buy a car, they will pay for electricity and food and travel inside Thailand. In other words, retirees come to Thailand to spend money. They are like year round tourists. They may not spend as much per week as regular tourists, but in a year they spend far more and they will spend money on the same things as middle class Thai's. This builds up infrastructure and business that all Thais use, spreading their spending to a much wider range of businesses than tourists do. It is a very healthy type of spending as opposed to only restaurants, hotels and bars.
Who will generate more sustainable and predictable economic benefit to Thailand: 100 billionaires or 1 million retirees?
Wealthy countries are not wealthy because of billionaires, they are wealthy because the middle class is large. Thailand would be far better off getting many, many retirees. They will bring in their money, they will spend it then, when they die, they will leave houses, infrastructure and money to their relatives and friends inside Thailand and that wealth will help the Thai economy long into the future.
Thailand needs a larger middle class. Import it.
My suggestion is
1. Long term retirement visas. At least five years. 10 would be better.
2. No 90 day reporting. I think yearly is a decent compromise to ensure legal residency/marriage in Thailand. For non-retirees rules may be different.
3. Yearly Medical Insurance fee for the government program as part of the visa, just like all Thais. If a retiree wants more, they can pay for more, just like Thais.
4. Ability to own a single personal residence and land of a maximum size (2-4 Rai say). The residence can be inherited by the owners children regardless of residence or citizenship. Retiree would feel more comfortable making this large investment and it would cut down on the fraud often associated with land and expats.
These changes would be enough for me to feel secure and to deeply commit to living in Thailand. But, I have a one year visa, so I plan one year at a time. Something I am reminded of every 90 days.