Given that you are a ski instructor and are likely to have have more leg/foot muscle development than the average person, you would "probably" be okay with the Premiere. Yes, it would absolutely be stiffer than what is required, but as far as it being so stiff that it will prevent proper ankle bend, only you would be able to determine that upon trying them on. If you can, while standing, bend your ankles and push your knees beyond your toes (vertically) then they will probably be fine.
slcbelle (also a ski instructor) started skating in Premiere's and while those boots didn't work out for a variety of reasons relating to fit, I don't think "too stiff" is one of the problems she had with them - initially they seemed to be fine. One of the problems she had, which is one that a lot of Jackson skaters with a wider foot report, is that as her boots broke in and the padding began to compress, her heel began to slip inside of her boot. I think (though it's possible I may be wrong!) that they were also a half size to full size too long as well, which only compounds the problem. Most of us with a wider ball have split width boots to compensate for the looser heel. Those who don't swear that their next pair will have it, or that they'll be trying another brand. I wear an E ball with a B heel, I could probably even consider an A heel, but I haven't yet experienced any heel slipping in my skates (currently or with my previous pair, also split width). Opting for a narrower heel is definitely something to discuss with your fitter - sometimes they can tell by looking at your feet if your heel is narrower in relation to the ball of your foot, sometimes it's simply trial and error (expensive trial and error, but on the flip side of that, once you know you need it, it's an easy modification to request, and I would expect that most people wearing a split width in one brand would continue to require it in another).
As far as blades, no reason you can't opt for something like the MK Professional, Wilson Coronation Ace, Ultima Legacy (or Matrix Legacy) or the Eclipse Mist. All of those blades are likely to be as high level as you would ever require (and can easily handle double jumps - some kids even do triples in them). Upgrading once you have solid spins and single jumps is just a personal preference, it's not a requirement, plus blades can often outlast boots, so you may even be able to move whatever blades you get now to your next pair.