Trouble with Morphing rig made using Auto Rig Pro + custom bones + constraints

Hi there.
I’m reaching out in desperate need of advice and/or help with what I’m aiming for.
What I am using: Auto Rig Pro, an addon for rigging, developed by Artell Blender.
What I am inspired by: Gamesforge did achieve a rig that could be morphed in some of their games (correct me if it wasn’t them), where a human could transform into a werewolf seamlessly.
What I want to achieve: A rig made with ARP that uses custom bones to control the body shape while retaining the animation basics so only tiny adjustments have to be taken while animating.

To give a concrete example: I have a horse rig which is moving just fine, completely rigged for the first portion of its purpose. I could also make the ARP bones get into a shape, I made it possible to look like a Thouroughbred horse, a Pony, a Foal and a Draft horse, plus additional head shape variations, height variations, etc.
My issue is that I cannot export this for usage into my game engine (Unity), because I cannot separate body shape, growth and motion animation from each other as easily, the rig is very error prone. My solution was to work with custom constraints and more custom bones that would act according to some drivers I set up that were measuring bone positions, rotations, or alike - following other bones, copying their scale, position, rotation according to those four main controller bones I set up which were: Age, Height, Draftiness, Maternity (for mares).
I have been working at this rig for over five months now. The issue is that with some of these constraints, the original ARP setup broke, so I had to re-adjust things like going to the nostr-bones and ticking boxes like unified scale. I had to set global positions to local or vice versa, change the applying of position from World to Local with Parent, etc.

Somewhere in between, I screwed up big time and I have had several meltdowns caused by this whole thing so far, but the functionality is vital for what I am trying to achieve. I need just one model that serves as a multi purpose shape. I don’t know where or whom to ask anymore because amongst the people I know, I am the one with the most knowledge, and others I feel wouldn’t lend me their time to figure this out properly. Should I go to someone else with my prototype who can set this up in a less chaotic fashion? Is there anything I can look up for my actual issue? I’ve skimmed through this thread just before posting here, yet I feel like it’s not entirely what I am aiming for, because I want to combine morphing with animation in this case. https://blenderartists.org/t/morphing-between-rigged-characters/1180292/13 Going through search engines with “ARP Morphing”, “Auto Rig Pro Morphing”, “Morphing Rig Community”, and alike gave me not really helpful results thus far.
I’d be happy for any hint in the right direction. I know it has been achieved before, motion with morphing combined, just probably not with just one rig and only one mesh. I’m tired of getting python traceback call errors because I did something I shouldn’t have done, once again.
Is there any community that actively works with morphing rigs? Anyone I can reach out to who got time and nerves to look at what I fabricated so far? Hopefully, there is.

Thanks for reading and any contribution.