I don't think you will miss a heated steering wheel if you a moving to so Cal. Also, why not just get heated seats and not the whole cold weather package....you won't need the headlight washers.
Also, you should plan on having to buy at least one full set of tires
during your lease term. Run flats don't wear as well as regular tires
I don't have the sport package on the 128 vert. I have had it on all my other BMWs. I like that the non sport run flats are higher profile than those that come with the sport package. On my 335 coupe, I had to get a full set of tires
one time during my lease term (10K/36 mos) and I also had to replace two rear tires
at other times due to damage sustained by hitting pot holes. Run flats are very expensive!
You will love the 1 series convertible. I find it 100 times more enjoyable to drive than the 335 and it is very reminiscent of my 2003 330 e46 convertible....which is a GREAT thing!
EDIT: Mine is also a stripper with no options but heated seats and BMW apps. I do wish it had premium package on it as I really miss the passenger side mirror that tilts down when you put the car in reverse. I thought this was standard on all bmws, but it is not. The regular halogens are terrific as well. Not as 'cool' looking as the xenons and without the xenons the led light bars in the tails don't illuminate nor does the eyebrow, but I'm OK with that.