I would echo focusing on shifting your bass drum work to your left foot and using your prosthetic to work your hi hat. Regardless of what ends up working for you... It will work for you and never stop! Unless you are constantly playing complicated hi hat patterns then you really only need to be able to go "up" and "down" with much less emphasis on any sort of controlled limb pivot to operate your hi hat stand effectively. You may have to get creative in your set up but that could be a fun opportunity to take a fresh look at drumming. All of this is a fresh opportunity, not a set back. You are on the path to continued success.
I´m sorry to hear about your problem and all the ones that had similar issues. Different options were presented already and I´m sure as everything evolves you will be able to find out the one that suits you better, I just wanted to add something else mostly from another point of view, this is also what I tell drummers that have no medical problems with their limbs but have a hard time playing the bass drum.
If you had read my previous posts most are around the same subject, "most drummers DON´T understand whats played on records or performances and try out nonsense techniques..."
Now, what i´m going to explain is not applicable to double bass drum technique, is for single pedal use ONLY.
Most drummers expend a lot of time practicing how to play 20.000.000 notes together as fast as they can when it is not the route. If you would be able to transcribe most great drummers you will notice that they just play 1 or 2 notes together with the bass drum at most. 3 in very extreme cases, but it is absolutely rare.
It´s about PLACEMENT, composition, etc. not speed. It´s about choosing the strategic points that make the pattern sound cool, hip.
So, as usual, the plan is to know music enough to be able to transcribe YOURSELF what the great drummer played to outline some rules for you to use, not to be fast. If you are fast it is a plus, granted, but the other is more important.
One note will be enough, in general you may need to play 3 of those SINGLE notes with the bass drum dispersed per 4/4 bar.
Remember, you usually have the freedom to shape rhythms and fills to showcase your best features, but you can only do that if you understand music.
So, indipendentenly of what you decide, think about this.
I'm glad you have this outlook, I would too.
Had a thought..
How about an adjusted seat height, so you foot/heel is more in a "floating" position and your thigh does a type of bounce for any doubles or multiple stroke you want to do?
There isn't anything that say's you "have to" do anything with the bass drum work, so doing what works for you is "enough" anyway, even though I am sure you will still want to improve as you would have before.
In getting used to the way things work for you now, you'll likely get faster naturally.
I'm just sitting here bouncing my leg and holding my ankle still and wondering how that would work with just my heel on the footboard....