Other Planet trucks COULD be suitable, but with several caveats.
First off lets look at your list of benefits.
Stable at speed: Yes, Very stable at speed. This is a valid reason to consider them. If you are only interested in this and not their steering characteristics you could get that by putting an Other Planet Truck only in the rear.
Change Cam Profiles for different truck feelings: Um, Technically this is true, but added practicality is pretty minimal. Its a nice thing to be able to do, but its talked about way more than its actually done.
Easy to swap hanger: This is an interesting idea. Hangers are pretty easy to swap for sure.
I never really swap hangers, I've never found it that practical. But using it to swap out motors... I could see that.
Could Standard Motor Mounts be used?: I do not think so. The hanger would be great to mount a motor onto, its got this nice flat side that would index really well. But... The baseplate is so wide, there's not a ton of space between the baseplate and the wheel. There's also an issue of interference with the baseplate as the trucks lean so far.
Definitely not impossible to mount a motor on there, but it would involve a clever solution, and you probably couldn't find an off the shelf option that would work. The trucks are pretty modifiable, and anybody willing to delve into that would have a lot of mounting options open up for them.
Has anyone ever tried to diy something similar?: Yes, there have been a small handful of people who have made their own OPs before referencing only pictures and video. And I'm really open and willing to help anybody wanting to do that with any answers they need.
Because the trucks can lean so far It could complicate the drive train.It would make belts running from the deck to the hanger troublesome I think. Hub motors would be by far the simplest way to circumvent the problem. Or, another way to circumvent the problem... If you're only looking for stability benefits put the OP on the rear, don't motorize it, and motorize the front truck instead.
As far as DIYing some OPs...
Here's something really cool, for the base plate all that matters are that the two walls are parallel, and for the hanger all that matters is that the two sides are parallel. How Thick the hanger is... doesn't matter. You want a 4" thick hanger? you just need the baseplate walls to be 4" apart. Cant imagine anybody wanting 4" thick hangers for anything, but if you were building your own you could fit anything you need to mount motors to in the hanger, easily.
Short of DIY, you also have some modification options.
The baseplate is big, and that is where a lot of the the problems start. You can actually cut the baseplate down to 3" wide, and use a different flatter cam to achieve a pretty similar feel to a 4" cam, and buy yourself a ton of extra space.
The axles are 1/2 steel in the hanger, so you can actually tap into them if you're very careful ( they're hardened ).
Final thoughts... How suitable they are I think really comes down to what you're wanting to get of your board.
When people ask me if they should get OPs I really drill them on what they're going to be trying to do with them and what they expect, and that same thing applies here. E-skate isn't a riding discipline.