To minimise tax exposure most of the revenue for the Philippine company was redirected to the HK company because of a loophole that allows foreign derived profits to be exempt from taxation in HK.

However all your properties will benefit from the additional marketing exposure by letting prospects know (give them a brochure or verbally mention the others) about the other offerings that they may have not been looking at in the first place.  

Alternately, some investors choose to forego the tax exposure and use the IRA in passive ways such as being a hard money lender to flippers or investing in rental income properties.So yes, there is a lot to learn, but once you get a handle on the framework of how a self-directed IRA fits into real estate investing, you should find that such a strategy can produce superior results for your retirement wealth building.

Is it a function of units or time or variety or spectrum of industry exposure?

If full authority it may be possible to avoid a court confirmation and exposure to over-bidding by competiting buyers.If no probate, buying the asset (the property) without a probate is tougher.

You will find that either your anticipated tax situation will likely not require as much help from a depreciation write off, or that your exposure now is not so bad that you can absorb the 140K or so in tax from a sale foregoing the 1031.If paying the tax now is too painful and you anticipate needing more depreciation write off in the future then 1031 and use the gain to purchase more property than you sold and take both the remaining 12 or so years on your current property basis and the additional depreciation you gain through purchasing up.

I'm sure it would make it easier but I wouldn't want that exposure.   

Again that is a business decision whether or not you want to pay the additional premium to cover those exposures. 

After 18 yrs I deduced my exposure was less that 1% probability and ultimately threw the S-corp and LLC overboard as excessive cost to maintain.

Your can still buy and, by choice, limit your exposure to college students.