How do you backport in Persona? Do you just use five attributes? (Aspect, Domain, Realm, Spirit, and Persona?)
Yes. If you glance at 2e and play it for a few sessions domain works pretty well. But if you look really hard at the system - which I did, since I overanalyze these things really hard - Domain tries to handle both creations of your actual estate and creations of associated concepts. However, this was only half-implemented, and the rulebook skipps it 90% of the time and mentions or alludes to it the other 10% of the time. The thing is:
If you allow domain to cover only the estate, then the noble of big can do all sorts of things with his domain, while the noble of elephants is probably specced into aspect or spirit or something because he can only create, change, and destroy elephants using domain.
If you allow domain to cover associated concepts, then the noble of elephants can do everything the noble of Big can do, and more, with his domain. So why would you be the noble of Big?
The most common implementation, that I've seen, is to focus on the actual estate but to allow associated concepts sometimes, if it makes sense and the HG likes it I guess? It gets really fiddly at time.
The obvious solution, to me, was to add Persona to 2e. Noble of Big takes domain, noble of elephants takes a 3-point estate property "Elephants are big" and specs into Persona, both can do stuff.
The 3E rules seem much more robust, in my opinion (although I'm still struggling to digest Will, Cool, Edge, Strike, etc.,)
You can have exchange of MP in 2e using the limitations system, so that's not the only real issue; the rulebook doesn't emphasize it as much, probably because there aren't a dozen different ways to do it. I didn't want to go too far into it in my last post, but I consider statting mortal bodies complete chaff in a system where Aspect 1 more than covers all of it.
I alluded to this in my previous post, but my biggest issue with 3e is that creativity got shut down in favor of "balance." Basically, here's how conflict worked in 2e:
My opponent has 5 spirit. If I wish to electrocute him, I need to perform a creation of electricity with 5 penetration (which gives him one wound*). If I wish to punch him, I probably just need to perform an aspect miracle that's higher than his aspect (which also gives him 1 wound). I can also solve the problem laterally: I can create a cage of stone or cement or rock around him, at a larger range than his auctoritas. However, the miracle takes a few second to become part of reality, so if I don't create the miracle with penetration 5, he can just move into range of it and his auctoritas will shred it. There are lateral solutions to this: For instance, I can create a cage high in the air that will solidify by the time it lands over him, assuming he doesn't move. If I perform a more complex miracle, perhaps invoking multiple estates, I can add remote-control thrusters to the cage to position it over him if he moves while it falls, then spend my prosaic action every round driving it. I can use a major miracle to make all of the air within one cubic kilometer flee the area, then another forming a boundary to keep it out; the air that was in side his auctoritas would then disperse into the vaccuum, depriving him of breath. Of course, it's low aspect to survive for a while without breathing.
There's things, however, that I can't do to a noble/excrucian/power in 2e. I can't teleport him, because his space and position do not belong to the estates of space or position. I can't freeze him because his time isn't part of the estate of time. I can't force his mouth closed, even if I penetrate his auctoritas, because his mouth does not belong to the estate of mouths (which is why the vacuum approach, above, is the best way to prevent someone from speaking). I can't alter his memories or erase his will. And so on. Do things to people; you can't alter them fundamentally. Think laterally.
Now let's get to 3e. I can perform the same aspect miracle (let's say I shoot him at aspect 6), giving him one wound. I can perform the same domain miracle (how about I electrocute him), giving him one wound. I can close his mouth, giving him one wound. I can slow his personal time down or alter his memories or shrink him down to 1 atom of size, giving him one wound. Basically, 3e conflates health to personal agency, so if I damage your ability to force your will upon the world (by shooting you, preventing you from speaking, caging you to prevent your movement, slowing down your actions....) then that's one "wound."
This is my largest problem with 3e. 2e focuses on creativity and problem-solving. 3e is a numbers fight, without the ability to meaningfully affect another power short of killing them.