It seems to me that all those who claim to ‘use the metric system’ don’t. If they did airspeed would be in m/s, fuel flow in kg/s, altitude in m etc. At least pressure is now in hectopascals (in the UK at least) so we are slowly getting there!

The messiest aircraft I’ve flown for units was a PA32 with fuel flow in US gal/hr. Fuel loaded in litres. W&B calculated in lbs. Lots of opportunities to get it wrong,

Despite I very much prefer the metric system in everyday life and as much better than the imperial/nautical system it is in engineering, feet for altitude is easier to count: 1, 2, 3, 4, 5 thousand feet etc. vs. 300, 600, 900, 1200, 1500 ... metres. 100 metres vertical spacing would be too close, 500 metres would be a waste of space and still not be as easy to count as thousands of feet.

Wether it's knots or kilometres per hour doesn't make much difference, but they should use the same unit for airspeed and wind speed (and distance of course). Kilometres per hour for airspeed and metres per second for wind speed doesn't make much sense imho. Using the same unit not only helps with speed vs. distance calculations but also roughly comparing a crosswind relative to airspeed without having to think too much.

For an untrained, earthbound person wind in m/s is very easy to understand.

It is, but everything in aviation is in kts.

As an ex met-man familiar with the mix [and a survivor of the deg F/deg C change] I regret to say that anything other than a total change to metric is ultimately to fart against thunder.
One is, however, stuck with awkward 360 degrees, 60 minutes, 24 hours. 7 day weeks and 12 month years. These, I suspect, are beyond redemption.

Having flown the Russian types around the world for many years I never had a issue with units conversion and qnh/qfe utilization in spite of equipment and rule difference. As my colleagues as well

Easier than having your heading indicator marked in radians. Imagine trying to maintain a heading of exactly pi :D

In this case it is 2900'

but if you have RMK QBB110 it means cloud base is 110 meters

Try operating into a Chinese airport a few hundred feet AMSL which uses QFE when you have an altimeter reading in feet and your company uses QNH. Basically you set QNH on the altimeter and have a conversion chart which gives you the number of feet to set on the FCU in response to the controller's instruction given in metres referenced to QFE. This chart is unique to the airport and obviously differs from the standard feet/metre conversion chart.

I agree, it's inconveniently but possible :)