Wow,
So many suggestions.
1. 2/32 is technically bald, there's no way of putting an exact mileage to how long they'll last.
2. There is nothing wrong with buying new tires at 4/32 (obviously you would want to buy a matching set of 4 at the same time, I'm using 4/32 because all 4 tires help with traction.
3. We are leasing our HL and besides changing out the drivers armrest to something wider I wouldn't put a penny besides oil changes, rotation and balance and alignments into a leased vehicle, you'll still be stuck with a set of wheels/tires at the end of the lease that might not fit your next vehicle.
4. Wheel purchases are based on individual aesthetics, it's better for you to come back with the brand/style you like and people can chime in with brand quality, there are hundreds of different companies out there. I for one, have always bought Konig's in 18s with a 225/40 18 tire and never had problems with them. If you do wind up upgrading I personally like the Yokohama Avid in 18, my 18" Avid H4s came with a 60k treadwear warranty.
5. The 90's called, they want these rims back, Niche misses them., btw OZ is a good brand, maybe look at TSW for some nice looking, good quality rims, in an OE style you like.
6. Even if you use the Miata Tire Calculator to keep your rolling diameter the same and therefore your odometer, an 18" wheel will still make your car look jacked up.
7. My perspective with modification is you do it right or not at all, if you put on rims you lower a car, if you do HIDs you do them in the proper housing, half @$$ modifications look like half @$$ modications. <~this last part is not directed at the original poster, just in general.
8. I would definitely go 18"+, I think my favorite wheels out there right now are the AT Italia Inox SS. My "ps" skills

, I think they look damn good on your car though
