RRoG + Aquila is a terrible option IMO... you might be able to get around this with an absolute ton of APoC, but otherwise, you'll have so much attack speed after you drop out of Archon that you'll drop below your Aquila threshold in seconds channeling Arcane Torrent. This is especially true when it's just the RG out, which is the time you really need your DR from Aquila to be working. However, APoC is worth exactly zero in Archon.
I was thinking about Endless Walk as an alternative to Hellfire/Maras + Halo and CoE, but first you need more than one Unity to make it work- not guaranteed on a seasonal character. IIRC there's a really sturdy Energy Armor rune you could consider using instead of Frost Armor since Halo is gone- that might help with Halo+Frost Armor's lack of helpfulness when taking the first hit. Endless Walk's always-on damage boost after a couple seconds of being stationary does sound a lot more reliable than CoE's insane damage boost 25% of the time, especially since the maximum level of the boost (100%) isn't variable like CoE's (160-200%) is.
Out of curiosity, what alternatives to the Furnace were you thinking of for the cube weapon slot?