If the national cricket teams of two nations not currently among the ICC "Test" nations were to meet and play a 5-day match according to test rules, what status would that match have? Could it be counted as a sanctioned international at all or would it be no better than two amateur village teams playing a 5-day match?

This is purely hypothetical. To my knowledge (and just researched) this type of match has never taken place since the formation of the International Cricket Council (ICC). An answer can only be speculative.

It is a long way from a 'village' cricket match to an international 'Test' match. There are currently 12 'full' Test playing members of the ICC.
https://en.wikipedia.org/wiki/List_of_International_Cricket_Council_members#Full_members

The road to full membership is demanding. It requires achieving 'associate' membership by meeting several criteria and then meeting further conditions to apply for 'full' membership.

In order for a nation to apply for associate membership they must meet 5 criteria given by the ICC:[12][13]

An appropriate domestic cricket structure.
A recognized administrative governing body.
Proper domestic cricket competitions.
At least two cricket grounds in the country.
A "National Development Plan" and an annual budget.

For an associate member to apply for full membership they must have the following in-addition to the above criteria:[12][13]

At least three appearances in men's Cricket World Cups or men's T20 World Cups in the last ICC men's hosts cycle.
Four wins against two or more full members over the last ICC men's hosts cycle.
At least one appearance in women's Cricket World Cup or women's T20 World Cup in the last ICC women's hosts cycle.
Currently present on the ICC Women's ODI Team Rankings.
If a member country (full or associate) fails to adhere to the ICC membership criteria, they will be suspended or expelled by the ICC.[14][15]

https://en.wikipedia.org/wiki/List_of_International_Cricket_Council_members

Therefore, if a five day match such a that proposed in the question was to take place, it would NOT be a 'Test' match. The match might possibly be 'sanctioned' by the ICC as, say, an 'exhibition' match but that has yet to be determined. However, IMVHO, I believe such a match would receive quite an amount of attention and would be considered as somewhat more than a 'village' game.

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BTW but not entirely off-topic, the ICC will shortly be testing (sorry) a rule change that will allow 4-day 'Test' matches (which, as a traditionalist, I find horrifying).