I think people are blowing it out of proportion. 2, it will eliminate weak agents from markets (In my Opinion)

These can usually be reduced or eliminated by absorbing a higher interest rate or buying out in upfront 'points.'

Like you mentioned the remaining credit is applied to the principle if you pay off the loan or refinance (which is likely, since you are probably going to refinance to eliminate the PMI in the next 1-4 years) as opposed to a permanent buydown where you cannot recoup the permanent buydown aka paying points. 

Thankfully, and it's no coïncidence, the places where I end up investing are great for lifestyle.My pricing criteria eliminates Canada, Northern Europe and Oceania.My tourism criteria eliminates Africa.I eliminate Asia, including and up to the Middle East because, in most countries, foreign owners are treated second-class and that has serious implications from a risk point of view.

This way, you will eliminate the custodian completely with its fees, red tape, etc.

Although there are numerous safeguards, contracts, escrows, that can be used to mitigate the additional risk, that risk can not be eliminated.

I think that, regardless of the deal you have with the seller, the primary lender that you refinance with may not like you having a 0% equity stake in the property, or very tiny equity position of less than 25%, and may require you to reduce or eliminate the "junior lien" or whatever you want to call it that is this seller carry item. 

At the same time the Biden-Harris administration wants to double the capital gains tax rate and they previously attempted to eliminate the 1031 tax deferred exchange for most investors.

Eliminate debt, establish a budget, and save.

Use your common sense and critical thinking to eliminate the "noise" (wrong/not practical information).