But what would be the Faith-scaling fire affinity in your scenario?

Flame Art is fine as it is, only thing missing is that "ancient" affinity you are talking about

Why not use flame art? I use flame art on my pyromancer. Good damage

occult is for people that use bleed builds when they need to fight something that imune to bleed

AR

Next you want us to say 'Sites of Grace' instead of 'Bonfires'.
Not happening.

it means the same thing. Attack Rating(AR) and Attack Power(AP).

Still gonna say AR, still gonna say bonfires, still gonna say souls, still gonna say estus
Deal with it

Right now flame art is just a straight upgrade to sacred since they do the same amount of damage and have the same scaling but fire is a much better damage type than holy

The problem is that madness and death blight wouldn't affect many enemies as most are automatons of some type (even the foot soldiers are animated dolls), so there'd be no point. As much as I'd love to have a rot-inflicting weapon, it would be too OP... imagine katanas (or other innate bleed weapons) with rot as well.

Those status are too strong to be able to be put on anything. imagine using the antspur rapier with innate rot + an ash of war that adds madness as base status with an active effect that adds sleep like poison moth flight adds poison. Now one weapon is Rot + Madness + Sleep, or take dual wielding curved swords 4 hit combos into account and 1 running attack would instantly apply one of those statuses. That would be ridiculous.

That would be broken especially the death build up

i guess the only option is to get st. trina's sword in caelid