I'm thinking hard of using good hockey skates for this. I like the idea of not having a raised heel, or an upwards bend along the boot length.
Two days ago I tried to spin and jump on hockey skates, without removing the blades. I hate toe picks, but discovered I've become totally dependent on them, and basically couldn't. Also, I need to avoid backwards leans.
So I need to remove the blades (harder to do on some hockey skates than others, and I need to remove the rivets), and adding my figure blades.
But maybe my current blade length is too long without raised heels? Because to some extent, it is the vertically projected length of the foot that should matter to blade length.
The person who runs the pro shop at Gardens Ice House in Laurel, MD, USA, pointed out to me today that hockey skates do have raised heels - in fact they have mostly been raised 3 cm higher than they used to be a few years ago. And they are roughly as high as figure skate heels. In the case of hockey skates, the "heel" is in the blade holder, rather than something that looks like a high heel, as in figure skates.
But where hockey and figure boot insole shapes differ is in the upwards bend near the ball of the foot. There is much less upwards bend in hockey boots.
Yesterday I bought used hockey boots: Bauer Vapor 500 model for $75, in very good condition, though the blade runners, which are easily replaced, have some wear. I showed them to him, and asked about heat molding - he said he would charge $50.
They only require 175 degrees F to heat mold - more or less achievable with some handheld hair driers.
I have previously been unwilling to use a regular home oven, because their temperature regulation is poor. But,
https://www.icewarehouse.com/lc/skates/how-to-bake-a-hockey-skate-at-home.htmlpoints out a fix - use an oven thermometer, and insert the boots after turning the oven off. Page gives very detailed directions.
I didn't have time to ask what he would charge to remove rivets, or whether he carries the bolts and nuts that could hold figure blades on hockey boots.