Still looking forward to a community inspired bike frame, i.e. "ChinerTown" (...to agree on a suitable name) official frame with UCI certification, on which all our needs are met 

That would be awesome. An enduro, a full suspension XC, a hardtail, a gravel, a climber, an aero or a TT ?
But then could we all agree on the specs ? 

In this case let's write them up: info@lightcarbon.com info@winowsports.com, i already did, maybe they will decide

Did some lobbying like this already decided some builders to start producing a model?

I just don't understand why would they use a two piece spindle instead of one piece. They just made it more complicated, more expensive to manufacture for no good reason.

Bearings are pressed on the spindle.
A setup that ensures a proper alignment compared to BB cups that sit in general in poorly machined and/or not aligned frames.
The load is then spread more evenly on the two bearings.
Making them live longer.

In the industry, this is an assembly when more precision is required, and to handle better both radial and axial load.

A crankset is always in two pieces anyway.
On others cranksets, on the junction between the crank arm and the spindle gets an orthogonal and heavy load, while here the arms and half spindles are one piece.
Which in theory ends stiffer, if we can ever feel it with our tiny hundreds watts capable legs 

...What do you think, should i try it?...

There are already many stories here about Mira
Go to the home page, and search for miracle there

https://chinertown.com/index.php?topic=3365.0

What about this carbon pony?
https://www.carbonda.com/road-frames/106.html

That's quite an aggressive geometry. There is one thread here with it. Other than that I haven't seen it, but it's also Carbonda. So it should be fine.

Max tires 25mm is tight

...I was also surprised how thin the downtube actually is. I would estimate it was ~1mm thick?

Yes, it's scary how thin some tubes are.
Did you epoxy the RivNuts ?
Or you just did leave them  dry?

Actually, the dust cap cannot sit flush with the head tube because it rotates with the handlebar. So every time you turn your handle it is going to grind against the tube...

Until the 1.5" tops were common, the cover was generally flush or grinding as you say.
And there was 0.25mm shims coming with the headset to put some space if needed.
Enough to not touch but not too much to expose the bearings.

... and a self built battery...

I was going to ask about the nice looking battery, until reading it is self built 
Congrats! Do you have some more details about it?

I would never have dared to rivet a carbon frame.
If you have some more details, I'm interested too.