Known sports podiatrists who work with skaters:
Dr Paul Meissner, in Cockeysville, MD, USA. He also plays hockey, and is the father of Olympic skater Kimmie Meissner. He may be the best known podiatrist for skaters in the DC area. I've known about a dozen people who were misfit for boots by the same person I was, and saw him to correct it.
Many local skaters and skate techs praise Jonathon P. Contompasis who practices in Wilmington, DE, Newark, DE, and Kennet Square, PA. He is a surgeon.
http://www.brandywinepodiatry.com/doctors-bio/jonathancontompasisdpm.htmlSomeone on skatingforums praised Dr. Michael Donato in Fredericksburg, VA, USA. (Another link.) He is also a hockey coach, and a surgeon.
https://www.rappahannockdpms.com/staffI don't have this problem. But people I have talked to who solved somewhat similar problems have mentioned various solutions. I assume you have already tried tape under the insole under the arch, to support the foot enough that it doesn't collapse much. That's basic, and very common. I have indeed heard some people some people who support the lateral side, but I don't understand that. Intuitively, it seems like you want to prevent the medial side foot collapse, by leaving no room for such a collapse. In other words, try to make up for a deficiency of internal support by providing external support. (Possibly augmented by moving the blade closer to the medial side, which is what most fitters do instead, though I decided I personally dislike the effects of such offsets. Maybe you have also tried squeezing the foot around the area that pronates (by adding moleskin to the sides of the boot, or by making an insole that wraps around the foot there, so there is no room to collapse - that seems extreme to me, and I wonder if it can be healthy, but one skater who had troubles, including both a high arch and pronation, reported some success at one point from this approach. And maybe you have tried moleskin higher up on the side of the boot, near the ankle, you collapse towards, and perhaps moleskin on the outside of the lower foot below that to create a torque to try to prevent that collapse.
Perhaps the right attitude is that you don't have a bad foot. You have a badly fit boot that doesn't provide you the support you need. Hopefully, you just need to find the right expert(s), and/or experiment yourself.
Did you try full custom fit boots, fit by the factory store fitter, or by someone the manufacturer recommends? A skate tech I knew used to recommend Harlick a lot, and several people recommended them to me because I too have a wide forefoot, and also have narrow heels and short toes, and one leg is longer than the other, so both foot bottoms tilt to the left, but some people on this board have gotten good custom fit boots from Avanta (in California - but perhaps they are worth a trip), which has a podiatrist on staff, who does custom fittings. If that is too hard to get to, they can also work from foot casts created by other podiatrists. Of course full custom boots are even more expensive than seeing a podiatrist. Some people find they have to do both, and maybe experiment themselves as well.
A Harlick fitter (Phil), who used to be Harlicks master boot maker, told me of a ballerina who wanted skate boots without an elevated heel, and they made her boots to meet that request. I don't know why - perhaps she wanted boots that were profiled more like ballet slippers or point shoes. I'm not sure if that applies to you. How well do shoes without an elevated heel work for you? If you did that, it is quite possible you would need to have your blades re-profiled by an expert skate tech, to keep the balance point/sweet spot (transition in rocker radius) near the balls of your feet, and to make sure you can still use your toe picks right.
BTW, some people claim wide forefoots are natural - that most babies are born with them before the start wearing narrow toed shoes. I have no idea whether that is true, and there is obviously some variety. Given a proper custom boot fit that matches the shape of your feet, wide forefeet shouldn't be a problem. To some extent, a good fitter can stretch the toebox to the sides to match. And if your heel is also narrower than the boot, you can add moleskin there to get a snug fit, or make an insole that wraps around the sides of the heel.