Can a Model A front hub be used, yes. Has it been done, yes. There are some pit falls in doing so. The inner T bearing is used and A outer bearing is used. The A hub is shorter then the T so the threaded part needs to be trimmed back and a new cotter pin hole has to be drilled. I recall reading that the outer bearing now will be riding on the threaded part. This would not be a first, people have used the A outer bearing in this location but I would not recommend it. If I was going to use an A type bearing in this location I would sleeve the threaded area where it rides and find a different outer bearing. I am not sure if the T outer bearing could be used, I think you would run out of threads before it was seated. There is some room to cut new threads but now you will be needing a left and right hand die $$.
The T wire wheel uses the hub center and studs for centering and support the A uses the studs and outer part of the brake drum for support. Then you still need to address the inner seal.
I had a pair of A hubs that at one time had been used on a T, the brake drum was trimmed to the allow the A wheel to have some support in that area.
The rear hubs, the T and A, the axle tapers, there is a size different. The Model A is larger and I would have to check more but might be shorter. So you cant just put the A hub on a T axle, then there are the brakes to contend with. Also, the A rear hubs are supported on the rear axle housing unlike the T that are inside the axle tube.
Lots of things can be done if you have a good shop, tools and skill.
Back to the front hubs, the T spindle arms can be used in the A hubs. I have read in several places about people using A spindle arms and A steering boxes on T frames for speedsters, I tried fitting a pair just to try it out and seem to work. That is about as far as I got.