about the aether chaos combination, it seems like a fitting theme. given that grim dawn seems to have a lot of conflict between aether and chaos. anyway, if you want to make aether/chaos themed build, iirc there are amulet and sword (twilight’s veil?) that gives +stats to aether and chaos simultaneously. the twilight’s veil sword looks pretty cool, and its a great symbolization of the duality of your reverend.
for the celestials/ascendants/symbols you want to choose:
chthon is obviously for chaos. solael also dabbles in chaos. . abomination can be considered as a representation of the corrup and wicked nature of chaos.
while aether is kinda tricky… since empyrion (who is the zeus of all grim dawn celestials) doesn’t grant bonus aether damage. kinda weird because the celestials have close affinity with aether dimension.
there’s rattosh, attak seru, and alladrah’s phoenix. they’re a good patron choice for aether theme build. but they feel more like ascendant beings rather than natural celestials imo.
spear of heavens might be worth nothing. though it’s not a deity/celestial being, more like a symbol of the celestials’ mastery over the aether realms and their zeus’ bolt upon those who dare to strike their chosen champions.
widow is a minor aether constellation worth mentioning too. this is just my personal theory, but i think the widow constellation represent the aetherial servants’ (yes, the aetherials that invades cairn and aetherials that stays in aetherhold) sorrow upon being abandoned/used as expendable assets by their master celestials after they do so much good work building many worlds for their masters. now the widow constellation shed tears (read:drop aetherial bombs) for those who understand its sorrows.
for the class combination, i think inquisitor should always be your primary choice (since it is the only class that have reliable aether & chaos rr, also supported by some nice aether/chaos skills). occultist, arcanist, necromance or oathkeeper would be your second mastery.
i’m not that good at crunching numbers, so i can’t help much in the min maxing department. but i fell that you should focus on one type of damage aether/chaos, while the other damage should only be for cosmetic purpose. i could be wrong though. its not out of possibility that there are some great aether/chaos builds out there. maybe apostate is the most viable choice here, i dunno. but it sure fits the theme almost perfectly.
edit: just for giggles, maybe try making a build revolving around the duality of beauty and uglyness or healthiness & sickness. like dryad + ghoul, ulo + affliction.