After a dozen+ deals, they trust their agent knows what they want, but they still make semi-annual trips to meet with their team, and lay eyes on their assets.  

I want to try for #5 and possibly #6 as well, but I am not sure if I should stick to a turnkey route (which has all worked out REALLY REALLY well) or try to buy a semi distressed property to renovate a bit.

Have a clear lease that describes what you expect of them and then inspect their unit annual/semi annually to ensure they are holding up their end of the bargain. 

[I do semi-annual inspections on every unit, announced at least 24 hours before.]I'm not sure if your rental is a SFR or not.  

Briefly mentioned above but very important is the semi sharing of space (in this case shared ceiling/floor) as well as outside. 

We got into a home that was pretty cluttered with things (semi-hoarderish property).  

Like you said, coming up with a semi-accurate value of adding an ADU is tricky due to the lower level of comps.

Some folks want to be semi-retired in 5 years, that's not me.

I have a rockstar team of contractors in the New York area which is why I want to keep it semi close to the city (hour or so out). 

What finish for the bathroom, eggshell or semi-gloss??