but i see no reason it wouldnt be conservative or otherwise consistent with GR

I'm assuming GR holds. Does it actually prove the field is conservative, or just irrotational? If it's irrotational and simply connected, then it's conservative, but if you stick a portal in it, it might not be.

I doubt you could maintain a knife edge thin aperture, it would all smooth out.

Portals don't need a knife edge. For example: Flight Through a Wormhole. You do need negative energy density or it will collapse, but that on its own shouldn't break conservation of energy.