Trebor, not sure if you care at all about this any more, but I wanted to shoot something out there.
And this is based a bit on my bias against the Phoenix Walker. And the fact that it doesn't have a lot going for it in PVE. Or in Empire.
But there are two giant vulnerabilities of the Phoenix Walker. It has to 1 - cross the terrain endgame, which is basically suicide, and 2 - it has a massive arc weakness, which seems like 1/2 of everything.
So... if I was to do something with this unit, assuming I got it early, I would go Assembly or Syndicate, and load it up like this:
1. Therian augmented legs
2. Arc Retaliation Defense * gives 2 arc resistance on top of damaging shields and stun
3. Purification Field
That is a cheap unit. Plus, it is faster, which allows it to take the hits and close the gap - WITHOUT being completely vulnerable while it does. When positioned, attackers have to get 3 hexes away before hitting it, or they are likely stunned. And it has a heal, which cleanses status effects. Still a bit weak, but versatile.
Then endgame:
1. Arc Retaliation Defense
2. Positron Arc Storm Projector
3. Positron Defense Shield * 6 arc resistance, closing the big arc gap. And otherwise just crazy good.
That is a tough unit. If we can assume +2 "well-built," and maybe 1 or additional armor from some landmark, we are talking now about 9 base armor, 3 base shields, and +8 arc resistance, sealing the biggest gap. Plus, it has a massive air/ground arc storm it can release on an arc channel, plus massive fire damage from its base attacks, amped up with +30% damage from mods. That is a tough unit that can maybe actually get through the killing field, and do something on the other side.
I still think the unit is 'meh,' and slow, but it might have a function.
I also REALLY like the idea of jetpacks, which might let you cross the field, though just once, and it has no additional value. The Arc shields are WAY better IMO.
Anyways, there it is.