Hello, not sure what you have experienced in the past year or so with your 5, but I am curious.
I just bought a 2014 5 and I believe it has Good years on it, I can't be certain because it is back at the dealer for the second time with that same vibration problem. I noted the issue after 68 miles on it. I wanted to make the dealer aware ASAP so that it is on record. It now has 400 miles on it and still doing it.
wheels were checked for balance the first time. I had gotten an email for a survey of the dealer for the new car experience. Well I gave some of them a good mark and some not so good. I specifically noted that they told me the "flat spots" would run themselves out after a few thousand miles. I could not believe that this brand new car vibrated more than my 1995 geo tracker does. Unacceptable I wrote in the survey.
The very next day (yesterday) I got a phone call from the dealers' owners' grandson telling me they were going to RECTify my problem. They had me come in and they swapped the tires and wheels off of a just received mazda 5, less than 7 days USA old. I was all excited. I left the dealer went up the road 2.25 miles turned around and dropped off the van. worse, these "new" "better" wheels and tires shook sooner and with more vigor than the originals.
So Now I wait till Monday to see what they will come up with. I have, by the way, copied your letter with hopes to not have to send a version of my own to Mazda. Ridiculous, seriously, if I wanted a car that drove this poorly I would have bought something for 1500 off craigslist and saved the rest of the money for renting a nice car once a month or something.