Are tenants willing to pay more for an upgraded kitchen, potlights, granite counters, etc.?

Stainless and granite in a rental was not by design lol. 

I know many people personally who have all the surface appearances like homes, cars, new granite stainless steel kitchens who are all neck deep in debt.

You don't need granite.

Installing cabinets is not hard.New corian or cheap granite counters about $1800.

If features means granite counter tops or other cosmetic things that are above comparable units then you need to forget about those "over improvements" and price your unit in line with other units in the same area.The fact you're getting showings tells me you're in the right ballpark. 

Hardwood floors,granite countertops,stainless steel appliances,new drywall and paint throughout.

Presuming they were renovated, were they Formica counters and vinyl floors or high end tile, granite and hardwood floors?

I can build an addition for about 120k that contains two "units" of 2bd/2.5ba each with lots of premium features (9.5' ceilings, acid-stained colorful concrete floors, radiant heating throughout, central air, LED lights, granite countertops, subway tile backsplash, carrara marble porcelain look-alike bathrooms, etc.)

I know this won't be a popular idea for those who believe in buying American made, but China has some awesome products for rehabbers that could be obtained at a fraction of the costs that we pay here in the US (especially helpful with higher end products, slab granite, ect....) but they require volume purchases and logistics might be a nightmare.