I would say a couple of thousand is unreasonable. Are you going to the Amazon for a year with no chance to recharge?
Not on Stellios Air 
I would not disagree and why I would find it reasonable to be permitted to take the equivalent of whats specified. Up to 15 devices, each with a 160Wh battery installed, and spare batteries stored together up to the equivelent of 2no. 160Wh batteries. Any more and the airline would be asking for trouble, in my view.
Amazon’s next year. 
This is not possible; if the battery is over 10Wh you are limited to two batteries only.
You are overthinking this.
I don’t think I am. I’m saying that it cannot be unlimited as long as it’s reasonable, which is what you’re saying. You say so long as it’s ‘reasonable’, but without providing a definition of what reasonable is.
15no. devices can be taken on board per passenger, each with up to 160Wh of battery power installed. They can be stowed in the Hold, unless again somewhere it is defined what is portable and what is not. You are then also allowed to take 2no. spare batteries as carry on between 100Wh and 160Wh. We agree that it would likely be seen as unreasonable to take 2000no. 19.8Wh batteries on board as carry-on (unless perhaps one is travelling to the Amazon), because each of them have a capacity less than 100Wh and I have suggested it would not be unreasonable to instead take the equivalent of 2no. 160Wh batteries as carry-on. If I went along with your unrestricted limitation, one could build a bomb and carry it onto the plane.
It doesn’t need an argument. Just my interpretation of the vague rules differs to yours. If they weren’t vague, people wouldn’t be asking the question. 
That’s not my interpretation though, it is established aviation law from the FAA, ICAO, and IATA.
IATA Dangerous Goods Regulations, Section 2.3.5.9 (Lithium Batteries)
ICAO Technical Instructions, Part 8
FAA Advisory Circulars (120-96A and related guidance)
That may be, illustarting how ambiguously worded the airline’s published rules are. 
1999 packed for the morning. Fingers crossed youre right. 
As an aside, the recent bans on powerbank carriage and usage (mostly Asia currently but is spreading) has produced laws and airline policies that directly interfere with drone batteries carry on.
Some internal Japanese airlines in theory now would make it prohibited to carry 2 x Air3s batteries for example.
Its currently a mess of mixed policies and laws being constantly down-revised and spreading in Asia at least.
(Im normally flying with 4 x Mini 3 batteries, 3 x Air3s batteries, a hefty (just below limit) power bank, a few DSLR batteries and quite commonly underwater video light Lithiums). Mostly stuffed into fleece and trouser pockets due to carry on bag weight limitations.