When I know a city but not county, I list it as "city, _____ county, state, country". I think this is more clear than the use of extra commas, and it has the advantage of sorting the unknown counties together, giving me a clear indication of where additional research would be helpful.
This is a very interesting idea. I encounter a situation where I know a city but not a county fairly frequently. What I do now is omit the county with no double comma. It's clear (to me, at least) what's going on because I always, always, always include the words county or parish to make clear the distinction between county or parish on the one hand and city and town on the other hand. So for example, I enter Atlanta, Georgia without a double comma for the missing county if I don't know which of Atlanta's multiple counties was the site of the event in question. But the "_______ County" convention for unknown counties would make things really clear without reading too badly in reports, e.g., Atlanta, _______ County, Georgia.
How do you enter independent cities that truly are not a part of any county (at least in modern times)? They are common in Virginia, but they also exist in other states. I simply omit the county with no double comma, which I believe to be technically accurate. But it does not distinguish very well between Richmond, Virginia where the county doesn't actually exist in modern times and Atlanta, Georgia where the county does exist but is unknown to me. Your "_______ County" convention would solve that problem very nicely.
I actually have never understood the proper way to enter places names in New York City with the five boroughs. I encounter records that do mention a county and records that don't mention a county.
I don't like for USA or United States to appear repetitively in my reports when the country is clear from context, which it nearly always is. I would like to be able to enter USA into my database and not print it in reports, but RM does not support doing so.
The country field is not very well standardized across genealogy in any case. For example, FamilySearch uses United States and ancestry.com uses USA. I find USA acceptable because it is technically correct, even as an abbreviation, and my experience from living for a couple of years in Europe suggests that USA is well known and commonly used there as a designation for my country. United States is just wrong as a place name, even though it's the FamilySearch standard, because many countries in the world are the United States of Something and because the official name of my country is United States of America, not United States.
I also include words such as Township, District, etc. in place names to clarify levels. There are many other words such as this that need to be included to clarify levels in place names, especially outside of the USA. But the FamilySearch place name standard does not support such level identifiers as a part of place names.
Historically accurate vs. modern place names are a problem, especially for geocoding. I think you need to be able to record both with each type of place name clearly identified as to whether it is historically accurate or modern. That way, you could indicate both the historically accurate place where the event occurred and where the evidence for the event was recorded, and the modern name and geocode to identify where to find the modern locale for the event. Neither RM nor genealogy writ large handles this situation very well.
Support for languages other than English and place names are a problem. How do I enter a place name as Germany and print it in French as Allemagne or in German as Deutschland or in Norwegian as Tyskland or in English as Germany?
Place names are a mess. Place name standards are a mess.