You stated " I literally own no metric tools."
What do you use for the 6mm bolts (10mm hex heads) that are common on our vans?
I have grown to be comfortable with metric system, but it has taken many years to get over the Asian version of metric bolt head sizes, vs. the European version.
Is it going to be the 8, 10, 12, 14, 16 set of wrenches; or 8 10 13, 15 17 set I grab?

It was not very many years ago, when major tool manufacturers did not even include a 16mm or an 18mm in a complete set.
Also the 16 and 18mm bolt heads are not a very close match for the SAE wrenches, and in some places ( like taking out the front seat with the storage box under it) no SAE wrench allowed adequate movement, once the slop was taken up.
Ahh, the Whitworth (BSW) system...a nut and bolt sizing system which seems to have mostly gotten lost in history.
The wrench that fit the bolt on a BSW standard 1/4" threaded bolt, was labelled 1/4. How unique! When I first saw wrenches that marked :"0BA" and "1BA" I did a double-take.
We 'Yanks' decided to supply our 1/4 inch threaded bolts with matching nuts which could be in different wrench sizes.
In a previous life, I worked on some old British sports cars...that was fun stuff!
Rod J.